Method for transmitting and receiving downlink control information in wireless communication system supporting device-to-device communication and device for the same

ABSTRACT

A method for transmitting and receiving downlink control information in a wireless communication system supporting device-to-device communication and a device for the same are disclosed. The method for receiving downlink control information in a wireless communication system supporting D2D (Device-to-Device) communication includes: receiving, by a UE, downlink control information for D2D communication from an eNB; transmitting, by the UE to a reception UE, D2D communication control information on a PSCCH (Physical Sidelink Control Channel) based on the downlink control information; and transmitting, by the UE to the reception UE, D2D communication data on a PSSCH (Physical Sidelink Shared Channel) based on the downlink control information, wherein the downlink control information may include: a hopping flag field indicating whether frequency hopping is applicable when transmitting the D2D communication control information and the D2D communication data; a PSCCH resource allocation (RA) field including scheduling information for the PSCCH; a first PSSCH RA field including scheduling information for the PSSCH in a frequency domain; a second PSSCH RA field including scheduling information for the PSSCH in a time domain; and a TPC (Transmission Power Control) field including transmission power information for the PSCCH and PSSCH.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method for transmitting and receiving downlinkcontrol information related to D2D (Device-to-Device) communication in awireless communication system supporting D2D communication, and a devicesupporting the same.

BACKGROUND ART

Mobile communication systems have been developed to provide voiceservices, while guaranteeing user activity. Service coverage of mobilecommunication systems, however, has extended even to data services, aswell as voice services, and currently, an explosive increase in traffichas resulted in shortage of resource and user demand for a high speedservices, requiring advanced mobile communication systems.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive Multiple Input MultipleOutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wide band, and device networking, have beenresearched.

DISCLOSURE Technical Problems

There has been a difficulty in configuring downlink control informationrelated to D2D communication in a single downlink control informationformat due to a large amount of control information, because bothscheduling assignment and D2D direct communication data transmissionthat a D2D transmission UE send to a D2D reception UE need to bescheduled.

Moreover, transmitting downlink control information for schedulingassignment and D2D direct communication data transmissions each assumesa heavy signaling burden.

An object of the present invention proposes a method for transmittingand receiving downlink control information in order to schedule bothscheduling assignment and D2D direct communication data that a D2Dtransmission UE send to a D2D reception UE.

It is to be understood that technical objects to be achieved by thepresent invention are not limited to the aforementioned technicalobjects and other technical objects which are not mentioned herein willbe apparent from the following description to one of ordinary skill inthe art to which the present invention pertains.

Technical Solution

According to one aspect of the present invention, a method for receivingdownlink control information in a wireless communication systemsupporting D2D (Device-to-Device) communication includes: receiving, bya UE, downlink control information for D2D communication from an eNB;transmitting, by the UE to a reception UE, D2D communication controlinformation on a PSCCH (Physical Sidelink Control Channel) based on thedownlink control information; and transmitting, by the UE to thereception UE, D2D communication data on a PSSCH (Physical SidelinkShared Channel) based on the downlink control information, wherein thedownlink control information may include: a hopping flag fieldindicating whether frequency hopping is applicable when transmitting theD2D communication control information and the D2D communication data; aPSCCH resource allocation (RA) field including scheduling informationfor the PSCCH; a first PSSCH RA field including scheduling informationfor the PSSCH in a frequency domain; a second PSSCH RA field includingscheduling information for the PSSCH in a time domain; and a TPC(Transmission Power Control) field including transmission powerinformation for the PSCCH and PSSCH.

According to another aspect of the present invention, a UE for receivingdownlink control information in a wireless communication systemsupporting D2D (Device-to-Device) communication includes: an RF (RadioFrequency) unit for transmitting and receiving radio signals; and aprocessor, the processor being configured to receive downlink controlinformation for D2D communication from an eNB, to transmit D2Dcommunication control information to a reception UE on a PSCCH (PhysicalSidelink Control Channel) based on the downlink control information, andto transmit D2D communication data to the reception UE on a PSSCH(Physical Sidelink Shared Channel) based on the downlink controlinformation, wherein the downlink control information may include: ahopping flag field indicating whether frequency hopping is applicablewhen transmitting the D2D communication control information and the D2Dcommunication data; a PSCCH resource allocation (RA) field includingscheduling information for the PSCCH; a first PSSCH RA field includingscheduling information for the PSSCH in a frequency domain; a secondPSSCH RA field including scheduling information for the PSSCH in a timedomain; and a TPC (Transmission Power Control) field includingtransmission power information for the PSCCH and PSSCH.

According to yet another aspect of the present invention, a method fortransmitting downlink control information in a wireless communicationsystem supporting D2D (Device-to-Device) communication includestransmitting, by an eNB to a UE, downlink control information for D2Dcommunication, wherein the downlink control information may include: ahopping flag field indicating whether frequency hopping is applicablewhen transmitting the D2D communication control information and the D2Dcommunication data; a PSCCH resource allocation (RA) field includingscheduling information for the PSCCH; a first PSSCH RA field includingscheduling information for the PSSCH in a frequency domain; a secondPSSCH RA field including scheduling information for the PSSCH in a timedomain; and a TPC (Transmission Power Control) field includingtransmission power information for the PSCCH and PSSCH.

According to a further aspect of the present invention, an eNB fortransmitting downlink control information in a wireless communicationsystem supporting D2D (Device-to-Device) communication includes: an RF(Radio Frequency) unit for transmitting and receiving radio signals; anda processor, the processor being configured to allow the eNB to transmitdownlink control information for D2D communication, wherein the downlinkcontrol information may include: a hopping flag field indicating whetherfrequency hopping is applicable when transmitting the D2D communicationcontrol information and the D2D communication data; a PSCCH resourceallocation (RA) field including scheduling information for the PSCCH; afirst PSSCH RA field including scheduling information for the PSSCH in afrequency domain; a second PSSCH RA field including schedulinginformation for the PSSCH in a time domain; and a TPC (TransmissionPower Control) field including transmission power information for thePSCCH and PSSCH.

Preferably, the PSCCH RA field may include index information forderiving the positions of resource regions for PSCCH transmission.

Preferably, the first PSSCH RA field may include a Resource IndicationValue (RIV) indicating a starting resource block index for PSSCHtransmission and a length in terms of allocated resource blocks.

Preferably, the second PSSCH RA field may include information indicatinga time resource pattern used for PSSCH transmission.

Preferably, the TPC field may comprise a first TPC field indicating thetransmission power for PSCCH and a second TPC field indicating thetransmission power for PSSCH.

Preferably, the downlink control information may further include anRX_ID field including identification information for the reception UE.

Preferably, the downlink control information may further include an MCSfield indicating MCS (Modulation Coding and Scheme) information forPSCCH and/or PSSCH transmission.

Preferably, the PSCCH RA field may include information indicating a timeresource pattern used for PSCCH transmission.

Preferably, the downlink control information may further include a DMRSCS field including DMRS (demodulation reference signal) CS (cyclicshift) information for demodulating the D2D communication controlinformation and/or D2D communication data.

Advantageous Effects

According to an embodiment of the present invention, it is possible tosmoothly transmit and receive downlink control information in order toschedule both a scheduling assignment and D2D direct communication datathat a D2D transmission UE send to a D2D reception UE, by properlyconfiguring the fields constituting the downlink control information.

It is to be understood that advantageous effects to be achieved by thepresent invention are not limited to the aforementioned advantageouseffects and other advantageous effects which are not mentioned hereinwill be apparent from the following description to one of ordinary skillin the art to which the present invention pertains.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 shows an example of the network structure of E-UTRAN (evolveduniversal terrestrial radio access network) to which the presentinvention may be applied.

FIG. 2 is a diagram for explaining physical channels used in a 3GPPLTE/LTE-A system to which the present invention may be applied and atypical signal transmission method using them.

FIG. 3 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

FIG. 4 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 5 shows the structure of a downlink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 6 shows the structure of an uplink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 7 is a diagram illustrating the structure of DCI format 0 in awireless communication system to which the present invention may beapplied.

FIG. 8 shows an example of a form in which the PUCCH formats are mappedto the PUCCH region of the uplink physical resource block in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 9 shows the structure of a CQI channel in the case of a normal CPin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 10 shows the structure of an ACK/NACK channel in the case of anormal CP in a wireless communication system to which an embodiment ofthe present invention may be applied.

FIG. 11 shows an example in which 5 SC-FDMA symbols are generated andtransmitted during one slot in a wireless communication system to whichan embodiment of the present invention may be applied.

FIG. 12 shows an example of component carriers and a carrier aggregationin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 13 shows an example of the structure of a subframe according tocross-carrier scheduling in a wireless communication system to which anembodiment of the present invention may be applied.

FIG. 14 is a diagram conceptually illustrating D2D communication in awireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 15 shows an example of various scenarios of D2D communication towhich a method proposed in this specification may be applied.

FIG. 16 is a diagram showing an example of a method for transmitting andreceiving D2D control information and D2D data, which is proposedaccording to an embodiment of the present invention.

FIG. 17 is a diagram showing another example of a method fortransmitting and receiving D2D control information and D2D data, whichis proposed according to an embodiment of the present invention.

FIG. 18 is a diagram showing yet another example of a method fortransmitting and receiving D2D control information and D2D data, whichis proposed according to an embodiment of the present invention.

FIG. 19 is a diagram showing an example of a method for configuring D2Dcontrol information depending on D2D transmission mode, which isproposed according to an embodiment of the present invention.

FIG. 20 is a diagram illustrating an example of the timing relationshipbetween SG reception and SA transmission in a D2D UE, which is proposedin this specification.

FIGS. 21 and 22 are a flowchart illustrating an example of the timingrelation between SG reception and SA transmission in D2D UE, which isproposed according to an embodiment of the present invention.

FIG. 23 is a diagram showing another example of the timing relationbetween SG reception and SA transmission in D2D UE, which are proposedaccording to an embodiment of the present invention.

FIG. 24 is a diagram showing yet another example of the timing relationbetween SG reception and SA transmission in D2D UE, which is proposedaccording to an embodiment of the present invention.

FIG. 25 is a diagram showing an example of the timing relation betweenD2D SA transmission and D2D data transmission, which is proposedaccording to an embodiment of the present invention.

FIG. 26 is a diagram showing another example of the timing relationbetween D2D SA transmission and D2D data transmission, which areproposed according to an embodiment of the present invention.

FIG. 27 is a diagram showing yet another example of the timing relationbetween D2D SA transmission and D2D data transmission, which is proposedaccording to an embodiment of the present invention.

FIG. 28 is a flowchart illustrating an example of a method fortransmitting and receiving D2D data, which is proposed according to anembodiment of the present invention.

FIGS. 29 to 32 are diagrams showing examples of methods for providingnotification of the locations of SA resources or D2D data resources orboth, which are proposed according to embodiments of the presentinvention.

FIG. 33 is a flowchart illustrating an example of a UE scheduling methodfor D2D transmission, which is proposed according to an embodiment ofthe present invention.

FIG. 34 is a diagram showing an example of a UE scheduling method forD2D transmission using RRC signaling, which is proposed according to anembodiment of the present invention.

FIG. 35 is a diagram showing an example of a UE scheduling method forD2D transmission using a physical layer channel, which is proposedaccording to an embodiment of the present invention.

FIG. 36 is a flowchart illustrating an example of a method forperforming an HARQ procedure for an SG, which is proposed in thisspecification.

FIG. 37 is a diagram showing a D2D operation procedure proposed in thisspecification and an example of a signaling transmission/receptionmethod related thereto.

FIGS. 38 to 41 are flowcharts showing examples of a method fortransmitting downlink control information according to an embodiment ofthe present invention.

FIGS. 42 to 50 are diagrams illustrating a downlink control informationformat according to an embodiment of the present invention.

FIG. 51 illustrates a block diagram of a wireless communication deviceaccording to an embodiment of the present invention.

MODE FOR INVENTION

Some embodiments of the present invention are described in detail withreference to the accompanying drawings. A detailed description to bedisclosed along with the accompanying drawings are intended to describesome exemplary embodiments of the present invention and are not intendedto describe a sole embodiment of the present invention. The followingdetailed description includes more details in order to provide fullunderstanding of the present invention. However, those skilled in theart will understand that the present invention may be implementedwithout such more details.

In some cases, in order to avoid that the concept of the presentinvention becomes vague, known structures and devices are omitted or maybe shown in a block diagram form based on the core functions of eachstructure and device.

In this specification, a base station has the meaning of a terminal nodeof a network over which the base station directly communicates with adevice. In this document, a specific operation that is described to beperformed by a base station may be performed by an upper node of thebase station according to circumstances. That is, it is evident that ina network including a plurality of network nodes including a basestation, various operations performed for communication with a devicemay be performed by the base station or other network nodes other thanthe base station. The base station (BS) may be substituted with anotherterm, such as a fixed station, a Node B, an eNB (evolved-NodeB), a BaseTransceiver System (BTS), or an access point (AP). Furthermore, thedevice may be fixed or may have mobility and may be substituted withanother term, such as User Equipment (UE), a Mobile Station (MS), a UserTerminal (UT), a Mobile Subscriber Station (MSS), a Subscriber Station(SS), an Advanced Mobile Station (AMS), a Wireless Terminal (WT), aMachine-Type Communication (MTC) device, a Machine-to-Machine (M2M)device, or a Device-to-Device (D2D) device.

Hereinafter, downlink (DL) means communication from an eNB to UE, anduplink (UL) means communication from UE to an eNB. In DL, a transmittermay be part of an eNB, and a receiver may be part of UE. In UL, atransmitter may be part of UE, and a receiver may be part of an eNB.

Specific terms used in the following description have been provided tohelp understanding of the present invention, and the use of suchspecific terms may be changed in various forms without departing fromthe technical sprit of the present invention.

The following technologies may be used in a variety of wirelesscommunication systems, such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), and Non-OrthogonalMultiple Access (NOMA). CDMA may be implemented using a radiotechnology, such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented using a radio technology, such asGlobal System for Mobile communications (GSM)/General Packet RadioService (GPRS)/Enhanced Data rates for GSM Evolution (EDGE). OFDMA maybe implemented using a radio technology, such as Institute of Electricaland Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802.20, or Evolved UTRA (E-UTRA). UTRA is part of a UniversalMobile Telecommunications System (UMTS). 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE) is part of an Evolved UMTS(E-UMTS) using evolved UMTS Terrestrial Radio Access (E-UTRA), and itadopts OFDMA in downlink and adopts SC-FDMA in uplink. LTE-Advanced(LTE-A) is the evolution of 3GPP LTE.

Embodiments of the present invention may be supported by the standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2, thatis, radio access systems. That is, steps or portions that belong to theembodiments of the present invention and that are not described in orderto clearly expose the technical spirit of the present invention may besupported by the documents. Furthermore, all terms disclosed in thisdocument may be described by the standard documents.

In order to more clarify a description, 3GPP LTE/LTE-A is chieflydescribed, but the technical characteristics of the present inventionare not limited thereto.

System in General

FIG. 1 shows an example of the network structure of E-UTRAN (evolveduniversal terrestrial radio access network) to which the presentinvention may be applied.

An E-UTRAN system is an advanced version of the existing UTRAN system,and may be a 3GPP LTE/LTE-A system, for example. E-UTRAN consists ofeNBs that provide a control plane protocol and a user plane protocol toUEs, and the eNBs are connected via the X2 interface. The X2 user planeinterface X2-U is defined between the eNBs. The X2-U interface providesnon-guaranteed delivery of user plane PDUs (packet data units). The X2control plane interface X2-CP is defined between two neighbor eNBs. TheX2-CP performs the following functions: context transfer between eNBs,control of user plane tunnels between a source eNB and a target eNB,transfer of handover-related messages, uplink load management and thelike. An eNB is connected to user equipment UE through a radio interfaceand is connected to an Evolved Packet Core (EPC) through the S1interface. The S1 user plane interface (S1-U) is defined between the eNBand the serving gateway (S-GW). The SI control plane interface (S1-MME)is defined between the eNB and the MME (Mobility Management Entity). TheS1 interface performs the following functions: EPS (Enhanced PacketSystem) Bearer Service Management function, NAS (Non-Access Stratum)Signaling Transport function, Network Sharing Function, MME Loadbalancing Function and the like. The S1 interface supports many-to-manyrelations between eNBs and MMEs/S-GWs.

FIG. 2 is a diagram for explaining physical channels used in a 3GPPLTE/LTE-A system to which the present invention may be applied and atypical signal transmission method using them.

When a UE is powered on from off or enters a new cell, the UE performsan initial cell search such as synchronization with an eNB (S201). Tothis end, the UE receives a primary synchronization channel (P-SCH) anda secondary synchronization channel (S-SCH) from the eNB tosynchronization with the eNB and acquire information such as a cell ID(identifier).

Thereafter, the UE may acquire broadcast information within the cell byreceiving a physical broadcast channel from the eNB. In the initial cellsearch step, the UE may monitor a downlink channel state by receivingdownlink reference signals (DL RS).

Upon completion of the initial cell search procedure, the UE may acquiremore detailed system information by receiving a physical downlinkcontrol channel (PDCCH) and a physical downlink shared channel (PDSCH)based on PDCCH information.

Afterwards, the UE may perform a random access procedure (S203 to S206)to complete the connection to the eNB. To this end, the UE may transmita preamble through a physical random access channel (PRACH) (S203) andreceive a response message to the preamble through the PDCCH and thePDSCH corresponding to the PDCCH (S204). In the case of contention-basedrandom access, the UE may perform a contention resolution procedure suchas transmission (S205) of an additional PRACH signal and reception(S206) of a PDCCH signal and a PDSCH signal corresponding to the PDCCHsignal.

After performing the above-described procedures, the UE may receive aPDCCH signal and/or a PDSCH signal (S207), as a general uplink/downlinksignal transmission procedure, and may then receive a physical uplinkshared channel (PUSCH) signal and/or a physical uplink control channel(PUCCH) signal (S208).

Control information the UE sends to the eNB is collectively referred toas uplink control information (UCI). The UCI includes HARQ (HybridAutomatic Retransmit reQuest)-ACK (Acknowledge)/NACK (Non-Acknowledge),SR (Scheduling Request), CQI (Channel Quality Indicator), PMI (PrecodingMatrix Indicator), RI (Rank Indication), etc.

In an LTE/LTE-A system, the UCI is generally carried on the PUCCH.However, when control information and traffic data are to be transmittedsimultaneously, the UCI may also be carried on the PUSCH. Additionally,the UCI may be aperiodically carried on the PUSCH according to arequest/indication from the network.

FIG. 3 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

3GPP LTE/LTE-A support a radio frame structure type 1 which may beapplicable to Frequency Division Duplex (FDD) and a radio framestructure which may be applicable to Time Division Duplex (TDD).

FIG. 3(a) illustrates the radio frame structure type 1. A radio frameconsists of 10 subframes. One subframe consists of 2 slots in a timedomain. The time taken to send one subframe is called a TransmissionTime Interval (TTI). For example, one subframe may have a length of 1ms, and one slot may have a length of 0.5 ms.

One slot includes a plurality of Orthogonal Frequency DivisionMultiplexing (OFDM) symbols in the time domain and includes a pluralityof Resource Blocks (RBs) in a frequency domain. In 3GPP LTE, OFDMsymbols are used to represent one symbol period because OFDMA is used indownlink. An OFDM symbol may be called one SC-FDMA symbol or symbolperiod. An RB is a resource allocation unit and includes a plurality ofcontiguous subcarriers in one slot.

FIG. 3(b) illustrates the frame structure type 2. The radio framestructure type 2 consists of 2 half frames. Each of the half framesconsists of 5 subframes, a Downlink Pilot Time Slot (DwPTS), a GuardPeriod (GP), and an Uplink Pilot Time Slot (UpPTS). One subframeconsists of 2 slots. The DwPTS is used for initial cell search,synchronization, or channel estimation in UE. The UpPTS is used forchannel estimation in an eNB and to perform uplink transmissionsynchronization with UE. The guard period is an interval in whichinterference generated in uplink due to the multi-path delay of adownlink signal between uplink and downlink is removed.

In the frame structure type 2 of a TDD system, an uplink-downlinkconfiguration is a rule indicating whether uplink and downlink areallocated (or reserved) to all subframes. Table 1 shows theuplink-downlink configuration.

TABLE 1 Downlink- Uplink- to-Uplink Downlink Switch-point Subframenumber configuration periodicity

0  5 ms 1  5 ms 2  5 ms 3 10 ms 4 10 ms 5 10 ms 6  5 ms

indicates data missing or illegible when filed

Referring to Table 1, in each subframe of the radio frame, “D” isindicative of a subframe for downlink transmission, “U” is indicative ofa subframe for uplink transmission, and “S” is indicative of a specialsubframe including three types of a DwPTS, GP, and UpPTS. Anuplink-downlink configuration may be classified into 7 types. Thepositions and/or number of downlink subframes, special subframes, anduplink subframe are different in each configuration.

A point of time at which a change is performed from downlink to uplinkor a point of time at which a change is performed from uplink todownlink is called a switching point. The periodicity of the switchingpoint means a cycle in which an uplink subframe and a downlink subframeare changed is identically repeated. Both 5 ms and 10 ms are supportedin the periodicity of a switching point. If the periodicity of aswitching point has a cycle of a 5 ms downlink-uplink switching point,the special subframe S is present in each half frame. If the periodicityof a switching point has a cycle of a 5 ms downlink-uplink switchingpoint, the special subframe S is present in the first half frame only.

In all the configurations, 0 and 5 subframes and a DwPTS are used foronly downlink transmission. An UpPTS and a subframe subsequent to asubframe are always used for uplink transmission.

Such uplink-downlink configurations may be known to both an eNB and UEas system information. An eNB may notify UE of a change of theuplink-downlink allocation state of a radio frame by transmitting onlythe index of uplink-downlink configuration information to the UEwhenever the uplink-downlink configuration information is changed.Furthermore, configuration information is kind of downlink controlinformation and may be transmitted through a Physical Downlink ControlChannel (PDCCH) like other scheduling information. Configurationinformation may be transmitted to all UEs within a cell through abroadcast channel as broadcasting information.

The structure of a radio frame is only one example. The number ofsubcarriers included in a radio frame or the number of slots included ina subframe and the number of OFDM symbols included in a slot may bechanged in various ways.

FIG. 4 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which an embodiment of the presentinvention may be applied.

Referring to FIG. 4, one downlink slot includes a plurality of OFDMsymbols in a time domain. It is described herein that one downlink slotincludes 7 OFDMA symbols and one resource block includes 12 subcarriersfor exemplary purposes only, and the present invention is not limitedthereto.

Each element on the resource grid is referred to as a resource element,and one resource block (RB) includes 12×7 resource elements. The numberof RBs NDL included in a downlink slot depends on a downlinktransmission bandwidth.

The structure of an uplink slot may be the same as that of a downlinkslot.

FIG. 5 shows the structure of a downlink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Referring to FIG. 5, a maximum of three OFDM symbols located in a frontportion of a first slot of a subframe correspond to a control region inwhich control channels are allocated, and the remaining OFDM symbolscorrespond to a data region in which a physical downlink shared channel(PDSCH) is allocated. Downlink control channels used in 3GPP LTEinclude, for example, a physical control format indicator channel(PCFICH), a physical downlink control channel (PDCCH), and a physicalhybrid-ARQ indicator channel (PHICH).

A PCFICH is transmitted in the first OFDM symbol of a subframe andcarries information about the number of OFDM symbols (i.e., the size ofa control region) which is used to transmit control channels within thesubframe. A PHICH is a response channel for uplink and carries anacknowledgement (ACK)/not-acknowledgement (NACK) signal for a HybridAutomatic Repeat Request (HARQ). Control information transmitted in aPDCCH is called Downlink Control Information (DCI). DCI includes uplinkresource allocation information, downlink resource allocationinformation, or an uplink transmission (Tx) power control command for aspecific UE group.

A PDCCH may carry information about the resource allocation andtransport format of a downlink shared channel (DL-SCH) (this is alsocalled an “downlink grant”), resource allocation information about anuplink shared channel (UL-SCH) (this is also called a “uplink grant”),paging information on a PCH, system information on a DL-SCH, theresource allocation of a higher layer control message, such as a randomaccess response transmitted on a PDSCH, a set of transmission powercontrol commands for individual UE within specific UE group, and theactivation of a Voice over Internet Protocol (VoIP), etc. A plurality ofPDCCHs may be transmitted within the control region, and UE may monitora plurality of PDCCHs. A PDCCH is transmitted on a single ControlChannel Element (CCE) or an aggregation of some contiguous CCEs. A CCEis a logical allocation unit that is used to provide a PDCCH with acoding rate according to the state of a radio channel. A CCE correspondsto a plurality of resource element groups. The format of a PDCCH and thenumber of available bits of a PDCCH are determined by an associationrelationship between the number of CCEs and a coding rate provided byCCEs.

An eNB determines the format of a PDCCH based on DCI to be transmittedto UE and attaches a Cyclic Redundancy Check (CRC) to controlinformation. A unique identifier (a Radio Network Temporary Identifier(RNTI)) is masked to the CRC depending on the owner or use of a PDCCH.If the PDCCH is a PDCCH for specific UE, an identifier unique to the UE,for example, a Cell-RNTI (C-RNTI) may be masked to the CRC. If the PDCCHis a PDCCH for a paging message, a paging indication identifier, forexample, a Paging-RNTI (P-RNTI) may be masked to the CRC. If the PDCCHis a PDCCH for system information, more specifically, a SystemInformation Block (SIB), a system information identifier, for example, aSystem Information-RNTI (SI-RNTI) may be masked to the CRC. A RandomAccess-RNTI (RA-RNTI) may be masked to the CRC in order to indicate arandom access response which is a response to the transmission of arandom access preamble by UE.

FIG. 6 shows the structure of an uplink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Referring to FIG. 6, the uplink subframe may be divided into a controlregion and a data region in a frequency domain. A physical uplinkcontrol channel (PUCCH) carrying uplink control information is allocatedto the control region. A physical uplink shared channel (PUSCH) carryinguser data is allocated to the data region. In order to maintain singlecarrier characteristic, one UE does not send a PUCCH and a PUSCH at thesame time.

A Resource Block (RB) pair is allocated to a PUCCH for one UE within asubframe. RBs belonging to an RB pair occupy different subcarriers ineach of 2 slots. This is called that an RB pair allocated to a PUCCH isfrequency-hopped in a slot boundary.

PDCCH (Physical Downlink Control Channel)

Control information carried on the PDCCH is referred to as downlinkcontrol information (DCI). In the PDCCH, the size and purpose of controlinformation may vary depending upon a DCI (downlink control indicator)format, and the size may also vary depending upon the coding rate.

Table 2 shows DCI in accordance with DCI format.

TABLE 2 DCI format Objectives 0 Scheduling of PUSCH 1 Scheduling of onePDSCH codeword 1A Compact scheduling of one PDSCH codeword 1BClosed-loop single-rank transmission 1C Paging, RACH response anddynamic BCCH 1D MU-MIMO 2 Scheduling of rank-adapted closed-loop spatialmultiplexing mode 2A Scheduling of rank-adapted open-loop spatialmultiplexing mode 3 TPC commands for PUCCH and PUSCH with 2 bit poweradjustments 3A TPC commands for PUCCH and PUSCH with single bit poweradjustments 4 the scheduling of PUSCH in one UL cell with multi- antennatransmission modeport

Referring to Table 2, DCI formats may include a format 0 for PUSCHscheduling, a format 1 for scheduling of one PDSCH codeword, a format 1Afor compact scheduling of one PDSCH codeword, a format 1C for verycompact scheduling of DL-SCH, a format 2 for PDSCH scheduling inclosed-loop spatial multiplexing mode, a format 2A for PDSCH schedulingin open-loop spatial multiplexing mode, formats 3 and 3A fortransmission of a TPC (transmission power control) command for an uplinkchannel, and a format 4 for PUSCH scheduling within one uplink cell in amulti-antenna port transmission mode.

The DCI format 1A may be used for PDSCH scheduling regardless of whichtransmission mode is set for UE.

The DCI format may be applicable independently for each UE, and PDCCHsof multiple UEs can be simultaneously multiplexed within a singlesubframe. The PDCCH consists of one control channel element (CCE) or anaggregation of several contiguous CCEs. The CCE is a logical assignmentunit used to provide the PDCCH with a coding rate depending on a radiochannel status. The CCE corresponds to 9 sets of REGs each including 4resource elements. An eNB may use {1, 2, 4, 8} CCEs to configure onePDCCH signal. Here, {1, 2, 4, 8} are referred to as CCE aggregationlevels. The number of CCEs used to transmit a specific PDCCH isdetermined by the eNB according to channel state. A PDCCH configuredaccording to each UE is interleaved and mapped to a control channelregion of each subframe and according to a CCE-to-RE mapping rule. ThePDCCH position may depend on the number of OFDM symbols for a controlchannel of each subframe, the number of PHICH groups, transmit antenna,frequency shift, etc.

As described above, channel coding is performed independently onmultiplexed PDCCHs of UEs and cyclic redundancy check (CRC) is appliedthereto. The CRC is masked with each UE's ID such that each UE canreceive a PDCCH allocated thereto. However, the eNB does not provideinformation about the location of a PDCCH corresponding to a UE in acontrol region assigned in a subframe. To receive a control channeltransmitted from the eNB, the UE finds the PDCCH assigned thereto bymonitoring a set of PDCCH candidates in a subframe because the UE cannotbe aware of the location of the PDCCH and the CCE set aggregation levelor DCI format used for the PDCCH. This is called blinding decoding (BD).Blind decoding may also be called blind detection or blind search. Blinddecoding is a method by which a UE de-masks a CRC with the ID thereofand checks for a CRC error to confirm whether the corresponding PDCCH isa control channel for the UE.

Hereinafter, information carried in DCI format 0 will be described.

FIG. 7 is a diagram illustrating the structure of DCI format 0 in awireless communication system to which the present invention may beapplied.

DCI format 0 is used for scheduling a PUSCH in an uplink cell.

Table 3 shows information carried in DCI format 0.

TABLE 3 Format 0 (Release 10) Format 0 (Release 8) Carrier Indicator(CIF) Flag for format 0/format Flag for format 0/format 1A 1Adifferentiation differentiation Hopping flag (FH) Hopping flag (FH)Resource block assignment (RIV) Resource block assignment (RIV) MCS andRV MCS and RV NDI (New Data Indicator) NDI (New Data Indicator) TPC forPUSCH TPC for PUSCH Cyclic shift for DM RS Cyclic shift for DM RS ULindex (TDD only) UL index (TDD only) Downlink Assignment Index (DAI)Downlink Assignment Index (DAI) CSI request (1 bit) CSI request (1 or 2bits: 2 bit is for multi carrier) SRS request Resource allocation type(RAT)

Referring to FIG. 7 and Table 3, information carried in DCI format 0 isas follows:

1) Carrier indicator—0 or 3 bit

2) Flag for format 0 and format 1 differentiation—1 bit. Value 0indicates DCI format 0 and value 1 indicates format 1A.

3) Frequency hopping flag—1 bit. In this field, the MSB (MostSignificant bit) of the corresponding resource allocation may be usedfor multi-cluster allocation if needed.

4) Resource block assignment and hopping resourceallocation—┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐ bits.

For PUSCH hopping in single-cluster allocation, N_(UL) _(_) _(hop) MSBbits are used to obtain the value of ñ_(PRB)(i). (┌log₂(N_(RB)^(UL)(N_(RB) ^(UL)+1)/2)┐−N_(UL) _(_) _(hop)) bits provide resourceallocation of the first slot in the uplink subframe. For non-hoppingPUSCH in single-cluster allocation, (┌log₂(N_(BR) ^(UL)(N_(BR)^(UL)+1)/2)┐) bits provide resource allocation in the uplink subframe.For non-hopping PUSCH in multi-cluster allocation, resource allocationinformation is obtained from the concatenation of the frequency hoppingflag field and the resource block assignment and hopping resourceallocation field, and

$\left\lceil {\log_{2}\left( \begin{pmatrix}\left\lceil {{N_{RB}^{UL}/P} + 1} \right\rceil \\4\end{pmatrix} \right)} \right\rceil$

bits provide resource allocation in the uplink subframe, where the valueof P depends on the number of downlink resource blocks.

5) MCS (Modulation and coding scheme) and RV (Redundancy Version)—5bits.

6) New data indicator—1 bit.

7) TPC (Transmit Power Control) command for PUSCH—2 bits.

8) CS (Cyclic Shift) for DMRS (demodulation reference signal) and OC/OCC(orthogonal cover/orthogonal cover code) index—3 bits.

9) UL index—2 bits. This field is present only for TDD operation withuplink-downlink configuration 0.

10) DAI (Downlink Assignment Index)—2 bits. This field is present onlyfor TDD operation with uplink-downlink configurations 1-6.

11) CSI (Channel State Information) request—1 or 2 bits. The 2-bit fieldapplies only when the corresponding DCI is UE-specifically mapped byC-RNTI (Cell-RNT1) to UEs that are configured with one or more downlinkcells.

12) SRS (Sounding Reference Signal) request—0 or 1 bit. This field canonly be present only when the scheduling PUSCH is UE-specifically mappedby C-RNTI.

13) Resource Allocation type—1 bit.

If the number of information bits in DCI format 0 is less than thepayload size of DCI format 1A (including any padding bits appended toDCI format 1A), zeros shall be appended to DCI format 0 until thepayload size equals that of DCI format 1A.

Uplink Resource Allocation

Two resource allocation schemes Type 0 and Type 1 are supported forPDCCH/EPDCCH with uplink DCI format (for example, DCI format 0).

The uplink DCI format supports the indication of uplink resourceallocation of a set of consecutive resource blocks (Type 0) and theindication of uplink resource allocation of two sets of consecutiveresource blocks (Type 1).

If the resource allocation type bit is not present in the uplink DCIformat, only Resource Allocation Type 0 is supported.

If the resource allocation type bit is present in the uplink DCI format,it indicates Resource Allocation Type 0 if its value is 0 and ResourceAllocation Type 1 if it has any other value than 0. The UE interpretsthe resource allocation field depending on the resource allocation typebit in the PDCCH/EPDCCH with uplink DCI format detected.

The resource allocation information for Uplink Resource Allocation Type0 indicates to a scheduled UE a set of contiguously allocated virtualresource block indices n_(VRB). A resource allocation field in thescheduling grant includes a resource indication value (RIV)corresponding to a starting resource block RB_(START) and a lengthL_(CRBs) in terms of contiguously allocated physical resource blocks.

If (L_(CRBs)−1)≤└N_(RB) ^(UL)/2┘, the RIV is defined by:

RIV=N _(RB) ^(DL)(L _(CRBs)−1)+RB_(start)  [Equation 1]

else

RIV=N _(BR) ^(UL)(N _(BR) ^(UL) −L _(CRBs)+1)+(N _(BR)^(UL)−1−RB_(START))  [Equation 2]

where N_(BR) ^(UL) denotes the total number of resource blocks RBs inthe uplink bandwidth.

Meanwhile, the resource allocation information for Uplink ResourceAllocation Type 1 indicates to a scheduled UE two sets of resourceblocks. Here, each of the two sets includes one or more consecutiveresource block groups RBGs. The RGB size is as shown in the followingTable 4.

TABLE 4 System Bandwidth RBG Size N_(RB) ^(UL) (P) ≤10 1 11-26 2 27-63 3 64-110 4

To indicate resource allocation, the combinatorial index r, whichcorresponds to a starting RBG index s₀ and last RBG index s₁−1 ofResource Block Set 1 and a starting RBG index s₂ and last RBG index s₃−1of Resource Block Set 2, is defined by the following Equation 3:

$\begin{matrix}{r = {\sum\limits_{i = 0}^{M - 1}{\langle\begin{matrix}{N - s_{i}} \\{M - i}\end{matrix}\rangle}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

where M=4, and n=┌N_(BR) ^(UL)/p┐+1.

Physical Uplink Control Channel (PUCCH)

The Uplink Control Information (UCI) transmitted through a PUCCH caninclude Scheduling Request (SR), HARQ ACK/NACK information, and downlinkchannel measurement information as shown below.

-   -   SR (Scheduling Request): used for requesting uplink UL-SCH        resources. SR is transmitted by On-Off Keying (OOK) scheme.    -   HARQ ACK/NACK: a signal responding to a downlink data packet on        a PDSCH. This signal indicates whether a downlink data packet        has successfully received or not. ACK/NACK 1 bit is transmitted        in response to a single downlink codeword while ACK/NACK 2 bits        are transmitted in response to two downlink codewords.    -   CSI (Channel State Information): feedback information about a        downlink channel. CSI can include at least one of a Channel        Quality Indicator (CQI), a Rank Indicator (RI), a Precoding        Matrix Indicator (PMI), and a Precoding Type Indicator (PTI).        For each subframe, 20 bits are used to represent the CSI.

HARQ ACK/NACK information may be generated depending on whether adownlink data packet on a PDSCH has been successfully decoded. In anexisting wireless communication system, 1 bit is transmitted as ACK/NACKinformation with respect to the transmission of downlink singlecodeword, and 2 bits are transmission as ACK/NACK information withrespect to the transmission of downlink 2 codewords.

Channel measurement information denotes feedback information related toa Multiple Input Multiple Output (MIMO) scheme and may include a ChannelQuality Indicator (CQI), a Precoding Matrix Index (PMI), and a RankIndicator (RI). Such channel measurement information may be commonlycalled a CQI.

In order to transmit a CQI, 20 bits may be used in each subframe.

A PUCCH may be modulated using a Binary Phase Shift Keying (BPSK) schemeand a Quadrature Phase Shift Keying (QPSK) scheme. Control informationfor a plurality of UEs may be transmitted through a PUCCH. If CodeDivision Multiplexing (CDM) is performed in order to distinguish thesignals of UEs from each other, a Constant Amplitude ZeroAutocorrelation (CAZAC) sequence of a length 12 is mostly used. TheCAZAC sequence has a characteristic in that a constant size (amplitude)is maintained in a time domain and a frequency domain. Accordingly, theCAZAC sequence has a property suitable for increasing coverage bylowering the Peak-to-Average Power Ratio (PAPR) or Cubic Metric (CM) ofUE. Furthermore, ACK/NACK information about downlink data transmissiontransmitted through a PUCCH is covered using an orthogonal sequence oran Orthogonal Cover (OC).

Furthermore, control information transmitted through a PUCCH may bedistinguished from each other using a cyclically shifted sequence havinga different Cyclic Shift (CS) value. The cyclically shifted sequence maybe generated by cyclically shifting a base sequence by a specific CSamount. The specific CS amount is indicated by a CS index. The number ofavailable CSs may be different depending on delay spread of a channel. Avariety of types of sequences may be used as the base sequence, and theCAZAC sequence is an example of the sequences.

Furthermore, the amount of control information that may be transmittedby UE in one subframe may be determined depending on the number ofSC-FDMA symbols which may be used to send the control information (i.e.,SC-FDMA symbols other than SC-FDMA symbols which are used to send aReference Signal (RS) for the coherent detection of a PUCCH).

In a 3GPP LTE system, a PUCCH is defined as a total of 7 differentformats depending on control information that is transmitted, amodulation scheme, and the amount of control information. The attributesof Uplink Control Information (UCI) transmitted according to each PUCCHformat may be summarized as in Table 4 below.

TABLE 4 PUCCH Format Uplink Control Information(UCI) Format 1 SchedulingRequest(SR)(unmodulated waveform) Format 1a 1-bit HARQ ACK/NACKwith/without SR Format 1b 2-bit HARQ ACK/NACK with/without SR Format 2CQI (20 coded bits) Format 2 CQI and 1- or 2-bit HARQ ACK/NACK (20 bits)for extended CP only Format 2a CQI and 1-bit HARQ ACK/NACK (20 + 1 codedbits) Format 2b CQI and 2-bit HARQ ACK/NACK (20 + 2 coded bits) Format 3HARQ ACK/NACK, SR, CSI (48 coded bits)

The PUCCH format 1 is used for SR-only transmission. In the case ofSR-only transmission, a not-modulated waveform is applied. This isdescribed in detail later.

The PUCCH format 1a or 1b is used to send HARQ ACK/NACK. If HARQACK/NACK is solely transmitted in a specific subframe, the PUCCH format1a or 1b may be used. Alternatively, HARQ ACK/NACK and an SR may betransmitted in the same subframe using the PUCCH format 1a or 1b.

PUCCCH format 2 is used for transmission of CQI, and PUCCH format 2a or2b is used for transmission of CQI and HARQ ACK/NACK. In the case ofextended CP, PUCCH format 2 may be used for transmission of CQI and HARQACK/NACK.

PUCCH format 3 is used for carrying an encoded UCI of 48 bits. PUCCHformat 3 can carry HARQ ACK/NACK about a plurality of serving cells, SR(if exists), and a CSI report about one serving cell.

FIG. 8 shows an example of a form in which the PUCCH formats are mappedto the PUCCH region of the uplink physical resource block in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

In FIG. 8, N_(BR) ^(UL) is indicative of the number of RBs in uplink,and 0, 1, . . . , N_(BR) ^(UL)−1 means the number of physical RBs.Basically, a PUCCH is mapped to both edges of an uplink frequency block.As shown in FIG. 8, the PUCCH format 2/2a/2b is mapped to a PUCCH regionindicated by m=0, 1. This may represent that the PUCCH format 2/2a/2b ismapped to RBs located at a band edge. Furthermore, the PUCCH format2/2a/2b and the PUCCH format 1/1a/1b may be mixed and mapped to a PUCCHregion indicated by m=2. Furthermore, the PUCCH format 1/1a/1b may bemapped to a PUCCH region indicated by m=3, 4, 5. UEs within a cell maybe notified of the number N_(RB) ⁽²⁾ of PUCCH RBs which may be used bythe PUCCH format 2/2a/2b through broadcasting signaling.

The PUCCH format 2/2a/2b is described below. The PUCCH format 2/2a/2b isa control channel for transmitting channel measurement feedback (i.e., aCQI, a PMI, and an RI).

The report cycle of channel measurement feedback (hereinafter commonlycalled “CQI information”) and a frequency unit (or frequency resolution)to be measured may be controlled by an eNB. In a time domain, a periodicor aperiodic CQI report may be supported. The PUCCH format 2 may be usedfor a periodic report, and a PUSCH may be used for an aperiodic report.In the case of an aperiodic report, an eNB may instruct UE to carry anindividual CQI report on a resource scheduled to transmit uplink data.

FIG. 9 shows the structure of a CQI channel in the case of a normal CPin a wireless communication system to which an embodiment of the presentinvention may be applied.

The SC-FDMA symbols 1 and 5 (i.e., the second and the sixth symbols) ofthe SC-FDMA symbols 0 to 6 of one slot are used to transmit ademodulation reference signal (DMRS), and the remaining SC-FDMA symbolsof the SC-FDMA symbols 0 to 6 of the slot may be used to CQIinformation. Meanwhile, in the case of an extended CP, one SC-FDMAsymbol (SC-FDMA symbol 3) is used for DMRS transmission.

In the PUCCH format 2/2a/2b, modulation by a CAZAC sequence issupported, and a QPSK-modulated symbol is multiplied by a CAZAC sequenceof a length 12. A Cyclic Shift (CS) of the sequence is changed between asymbol and a slot. Orthogonal covering is used for a DMRS.

A reference signal (DMRS) is carried on 2 SC-FDMA symbols that belong to7 SC-FDMA symbols included in one slot and that is spaced at 3 SC-FDMAsymbols. CQI information is carried on the remaining 5 SC-FDMA symbolsof the 7 SC-FDMA symbols. Two RSs are used in one slot in order tosupport high-speed UE. Furthermore, UEs are distinguished from eachother using Cyclic Shift (CS) sequences. CQI information symbols aremodulated into all SC-FDMA symbols and transferred. The SC-FDMA symbolsconsist of one sequence. That is, UE modulates a CQI using each sequenceand sends the CQI.

The number of symbols which may be transmitted in one TTI is 10, and themodulation of CQI information is determined up to QPSK. If QPSK mappingis used for an SC-FDMA symbol, a CQI value of 10 bits may be carried onone slot because a CQI value of 2 bits may be carried on the SC-FDMAsymbol. Accordingly, a CQI value having a maximum of 20 bits may becarried on one subframe. Frequency domain spread code is used to spreadCQI information in a frequency domain.

A CAZAC sequence (e.g., ZC sequence) of a length 12 may be used as thefrequency domain spread code. Control channels may be distinguished fromeach other by applying CAZAC sequences having different cyclic shiftvalues. IFFT is performed on frequency domain-spread CQI information.

12 different UEs may be subjected to orthogonal multiplexing on the samePUCCH RB by 12 cyclic shifts having the same interval. In the case of anormal CP, a DMRS sequence on the SC-FDMA symbols 1 and 5 (on an SC-FDMAsymbol 3 in the case of an extended CP) are similar to a CQI signalsequence on a frequency domain, but modulation, such as CQI information,is not applied to the DMRS sequence.

UE may be semi-statically configured by higher layer signaling so thatit periodically reports different CQI, PMI and RI Types on PUCCHresources indicated by PUCCH resource indices n_(PUCCH)^((1,{tilde over (p)})), n_(PUCCH) ^((2,{tilde over (p)})), andn_(PUCCH) ^((3,{tilde over (p)})). In this case, the PUCCH resourceindex n_(PUCCH) ^((2,{tilde over (p)})) is information indicative of aPUCCH region that is used to transmit the PUCCH format 2/2a/2b and thevalue of a Cyclic Shift (CS) to be used.

Hereinafter, the PUCCH format 1a and 1b is described below.

In the PUCCH format 1a/1b, a symbol modulated using a BPSK or QPSKmodulation scheme is multiplied by a CAZAC sequence of a length 12. Forexample, the results of a modulation symbol d(0) by a CAZAC sequencer(n)(n=0, 1, 2, . . . , N−1) of a length N become y(0), y(1), y(2), . .. , y(N−1). The symbols y(0), . . . , y(N−1) may be called a block ofsymbols. After the modulation symbol is multiplied by the CAZACsequence, block-wise spread using an orthogonal sequence is applied.

A Hadamard sequence of a length 4 is used for common ACK/NACKinformation, and a Discrete Fourier Transform (DFT) sequence of a length3 is used for shortened ACK/NACK information and a reference signal.

In the case of an extended CP, a Hadamard sequence of a length 2 is usedin a reference signal.

FIG. 10 shows the structure of an ACK/NACK channel in the case of anormal CP in a wireless communication system to which an embodiment ofthe present invention may be applied.

FIG. 10 illustrates a PUCCH channel structure for transmitting HARQACK/NACK without a CQI.

A Reference Signal (RS) is carried on 3 contiguous SC-FDMA symbol thatbelong to 7 SC-FDMA symbols included in one slot and that are placed ina middle portion, and an ACK/NACK signal is carried on the remaining 4SC-FDMA symbols of the 7 SC-FDMA symbols.

Meanwhile, in the case of an extended CP, an RS may be carried on 2contiguous symbols placed in the middle of one slot. The number andpositions of symbols used in an RS may be different depending on controlchannels, and the number and positions of symbols used in an ACK/NACKsignal associated with the control channels may be changed depending onthe number and positions of symbols used in the RS.

ACK information (not-scrambled state) of 1 bit and 2 bits may berepresented as one HARQ ACK/NACK modulation symbol using respective BPSKand QPSK modulation schemes. Positive ACK (ACK) may be encoded as “1”,and negative ACK (NACK) may be encoded as “0”.

When a control signal is to be transmitted within an allocatedbandwidth, two-dimensional spreading is applied in order to increasemultiplexing capacity. That is, in order to increase the number of UEsor the number of control channels that may be multiplexed, frequencydomain spreading and time domain spreading are used at the same time.

In order to spread an ACK/NACK signal in a frequency domain, a frequencydomain sequence is used as a base sequence. A Zadoff-Chu (ZC) sequencewhich is one of CAZAC sequences, may be used as the frequency domainsequence. For example, by applying a different Cyclic Shift (CS) to a ZCsequence which is a base sequence, different UEs or different controlchannels may be multiplexed. The number of CS resources supported in aSC-FDMA symbol for PUCCH RBs for transmitting HARQ ACK/NACK isconfigured by a cell-specific upper layer signaling parameter Δ_(shift)^(PUCCH).

An ACK/NACK signal spread in a frequency domain is spread in a timedomain using orthogonal spreading code. A Walsh-Hadamard sequence or DFTsequence may be used as the orthogonal spreading code. For example, anACK/NACK signal may be spread for 4 symbols using an orthogonal sequencew0, w1, w2, or w3 of a length 4. Furthermore, an RS is also spread usingan orthogonal sequence of a length 3 or length 2. This is calledOrthogonal Covering (OC).

A plurality of UEs may be multiplexed using a Code Division Multiplexing(CDM) method using CS resources in a frequency domain and OC resourcesin a time domain, such as those described above. That is, ACK/NACKinformation and RSs of a large number of UEs may be multiplexed on thesame PUCCH RB.

The number of spreading code supported for ACK/NACK information isrestricted by the number of RS symbols with respect to such time domainspreading CDM. That is, the multiplexing capacity of an RS is smallerthan the multiplexing capacity of ACK/NACK information because thenumber of SC-FDMA symbols for RS transmission is smaller than the numberof SC-FDMA symbols for ACK/NACK information transmission.

For example, in the case of a normal CP, ACK/NACK information may betransmitted in 4 symbols. 3 pieces of orthogonal spreading code not 4are used for ACK/NACK information. The reason for this is that only 3pieces of orthogonal spreading code may be used for an RS because thenumber of symbols for RS transmission is limited to 3.

In case that 3 symbols of one slot may be used for RS transmission and 4symbols of the slot may be used for ACK/NACK information transmission ina subframe of a normal CP, for example, if 6 Cyclic Shifts (CSs) may beused in a frequency domain and 3 Orthogonal Cover (OC) resources may beused in a time domain, HARQ ACK from a total of 18 different UEs may bemultiplexed within one PUCCH RB. In case that 2 symbols of one slot areused for RS transmission and 4 symbols of one slot are used for ACK/NACKinformation transmission in a subframe of an extended CP, for example,if 6 CSs may be used in a frequency domain and 2 OC resources may beused in a time domain, HARQ ACK from a total of 12 different UEs may bemultiplexed within one PUCCH RB.

The PUCCH format 1 is described below. A Scheduling Request (SR) istransmitted in such a way as to make a request or does not make arequest that UE is scheduled. An SR channel reuses an ACK/NACK channelstructure in the PUCCH format 1a/1b and consists of an On-Off Keying(OKK) method based on an ACK/NACK channel design. An RS is nottransmitted in the SR channel. Accordingly, a sequence of a length 7 isused in the case of a normal CP, and a sequence of a length 6 is used inthe case of an extended CP. Different cyclic shifts or orthogonal coversmay be allocated to an SR and ACK/NACK. That is, in order to send apositive SR, UE sends HARQ ACK/NACK through a resource allocated for theSR. In order to send a negative SR, UE sends HARQ ACK/NACK through aresource allocated for ACK/NACK.

An enhanced-PUCCH (e-PUCCH) format is described below. An e-PUCCH maycorrespond to the PUCCH format 3 of an LTE-A system. A block spreadingscheme may be applied to ACK/NACK transmission using the PUCCH format 3.

Unlike in the existing PUCCH format 1 series or 2 series, the blockspreading scheme is a method of modulating control signal transmissionusing an SC-FDMA method. As shown in FIG. 10, a symbol sequence may bespread in a time domain using Orthogonal Cover Code (OCC) andtransmitted. By using OCC, the control signals of a plurality of UEs maybe multiplexed on the same RB. In the case of the PUCCH format 2, onesymbol sequence is transmitted in a time domain, and the control signalsof a plurality of UEs are multiplexed using a Cyclic Shift (CS) of aCAZAC sequence. In contrast, in the case of a block spreading-basedPUCCH format (e.g., the PUCCH format 3), one symbol sequence istransmitted in a frequency domain, and the control signals of aplurality of UEs are multiplexed using time domain spreading using OCC.

FIG. 11 shows an example in which 5 SC-FDMA symbols are generated andtransmitted during one slot in a wireless communication system to whichan embodiment of the present invention may be applied.

FIG. 11 shows an example in which 5 SC-FDMA symbols (i.e., a data part)are generated using OCC of a length=5 (or SF=5) in one symbol sequenceduring 1 slot and transmitted. In this case, 2 RS symbols may be usedduring the 1 slot.

In the example of FIG. 11, the RS symbols may be generated from a CAZACsequence to which a specific CS value has been applied and may betransmitted in a form in which a specific OCC may be applied (ormultiplied) to a plurality of RS symbols. Furthermore, in the example ofFIG. 8, assuming that 12 modulation symbols are used in each OFDM symbol(or SC-FDMA symbol) and each of the modulation symbols is generated byQPSK, a maximum number of bits capable of being transmitted in one slotare 12×2=24 bits. Accordingly, a total number of bits capable of beingtransmitted in 2 slots are 48 bits. As described above, if a PUCCHchannel structure using a block spreading method is used, controlinformation having an extended size compared to the existing PUCCHformat 1 series and 2 series can be transmitted.

General Carrier Aggregation

A communication environment taken into consideration in embodiments ofthe present invention includes a multi-carrier support environment. Thatis, a multi-carrier system or Carrier Aggregation (CA) system that isused in an embodiment of the present invention refers to a system inwhich one or more Component Carriers (CCs) having a smaller bandwidththan a target bandwidth are aggregated and used when the target widebandis configured in order to support a wideband.

In an embodiment of the present invention, a multi-carrier means of anaggregation of carriers (or a carrier aggregation). In this case, anaggregation of carriers means both an aggregation between contiguouscarriers and an aggregation between discontiguous (or non-contiguous)carriers. Furthermore, the number of CCs aggregated between downlink anduplink may be different. A case where the number of downlink CCs(hereinafter called “DL CCs”) and the number of uplink CCs (hereinaftercalled “UL CCs”) are the same is called a symmetric aggregation. A casewhere the number of DL CCs is different from the number of UL CCs iscalled an asymmetric aggregation. Such the term of a carrier aggregationmay be replaced with terms, such as a carrier aggregation, bandwidthaggregation, or spectrum aggregation.

An object of a carrier aggregation configured by aggregating two or morecomponent carriers is to support up to a 100 MHz bandwidth in an LTE-Asystem. When one or more carriers having a smaller bandwidth than atarget bandwidth are aggregated, the bandwidth of the aggregatedcarriers may be restricted to a bandwidth which is used in an existingsystem in order to maintain backward compatibility with an existing IMTsystem. For example, in an existing 3GPP LTE system, {1.4, 3, 5, 10, 15,20} MHz bandwidths may be supported. In a 3GPP LTE-advanced system(i.e., LTE-A), bandwidths greater than the bandwidth 20 MHz may besupported using only the bandwidths for a backward compatibility withexisting systems. Furthermore, in a carrier aggregation system used inan embodiment of the present invention, new bandwidths may be definedregardless of the bandwidths used in the existing systems in order tosupport a carrier aggregation.

An LTE-A system uses the concept of a cell in order to manage radioresources.

The aforementioned carrier aggregation environment may also be called amulti-cell environment. A cell is defined as a combination of a pair ofa downlink resource (DL CC) and an uplink resource (UL CC), but anuplink resource is not an essential element. Accordingly, a cell mayconsist of a downlink resource only or a downlink resource and an uplinkresource. If specific UE has a single configured serving cell, it mayhave 1 DL CC and 1 UL CC. If specific UE has two or more configuredserving cells, it has DL CCs corresponding to the number of cells, andthe number of UL CCs may be the same as or smaller than the number of DLCCs.

In some embodiments, a DL CC and an UL CC may be configured in anopposite way. That is, if specific UE has a plurality of configuredserving cells, a carrier aggregation environment in which the number ofUL CCs is greater than the number of DL CCs may also be supported. Thatis, a carrier aggregation may be understood as being an aggregation oftwo or more cells having different carrier frequency (the centerfrequency of a cell). In this case, the “cell” should be distinguishedfrom a “cell”, that is, a region commonly covered by an eNB.

A cell used in an LTE-A system includes a Primary Cell (PCell) and aSecondary Cell (SCell). A PCell and an SCell may be used as servingcells. In the case of UE which is in an RRC_CONNECTED state, but inwhich a carrier aggregation has not been configured or which does notsupport a carrier aggregation, only one serving cell configured as onlya PCell is present. In contrast, in the case of UE which is in theRRC_CONNECTED state and in which a carrier aggregation has beenconfigured, one or more serving cells may be present. A PCell and one ormore SCells are included in each serving cell.

A serving cell (PCell and SCell) may be configured through an RRCparameter. PhysCellId is the physical layer identifier of a cell and hasan integer value from 0 to 503. SCellIndex is a short identifier whichis used to identify an SCell and has an integer value of 1 to 7.ServCellIndex is a short identifier which is used to identify a servingcell (PCell or SCell) and has an integer value of 0 to 7. The value 0 isapplied to a PCell, and SCellIndex is previously assigned in order toapply it to an SCell. That is, in ServCellIndex, a cell having thesmallest cell ID (or cell index) becomes a PCell.

A PCell means a cell operating on a primary frequency (or primary CC). APCell may be used for UE to perform an initial connection establishmentprocess or a connection re-establishment process and may refer to a cellindicated in a handover process. Furthermore, a PCell means a cell thatbelongs to serving cells configured in a carrier aggregation environmentand that becomes the center of control-related communication. That is,UE may receive a PUCCH allocated only in its PCell and send the PUCCHand may use only the PCell to obtain system information or to change amonitoring procedure. An Evolved Universal Terrestrial Radio AccessNetwork (E-UTRAN) may change only a PCell for a handover procedure usingthe RRC connection reconfiguration (RRCConnectionReconfiguration)message of a higher layer including mobility control information(mobilityControllnfo) for UE which supports a carrier aggregationenvironment.

An SCell may mean a cell operating on a secondary frequency (orsecondary CC). Only one PCell is allocated to specific UE, and one ormore SCells may be allocated to the specific UE. An SCell may beconfigured after RRC connection is established and may be used toprovide additional radio resources. A PUCCH is not present in theremaining cells, that is, SCells that belong to serving cells configuredin a carrier aggregation environment and that do not include a PCell.When adding an SCell to UE supporting a carrier aggregation environment,an E-UTRAN may provide all types of system information related to theoperation of a related cell in the RRC_CONNECTED state through adedicated signal. A change of system information may be controlled byreleasing and adding a related SCell. In this case, the RRC connectionreconfiguration (RRCConnectionReconfigutaion) message of a higher layermay be used. An E-UTRAN may send dedicated signaling having a differentparameter for each UE instead of broadcasting within a related SCell.

After an initial security activation process is started, an E-UTRAN mayconfigure a network including one or more SCells by adding to a PCellthat is initially configured in a connection establishing process. In acarrier aggregation environment, a PCell and an SCell may operaterespective component carriers. In the following embodiments, a PrimaryComponent Carrier (PCC) may be used as the same meaning as a PCell, anda Secondary Component Carrier (SCC) may be used as the same meaning asan SCell.

FIG. 12 shows an example of component carriers and a carrier aggregationin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 12a shows the structure of a single carrier used in an LTE system.A component carrier includes a DL CC and an UL CC. One component carriermay have a frequency range of 20 MHz.

FIG. 12b shows the structure of a carrier aggregation used in an LTE-Asystem. FIG. 12b shows an example in which 3 component carriers eachhaving a frequency size of 20 MHz have been aggregated. Three DL CCs andthree UL CCs have been illustrated in FIG. 12, but the number of DL CCsand UL CCs is not limited. In the case of a carrier aggregation, UE maymonitor 3 CCs at the same time, may receive downlink signal/data, andmay transmit uplink signal/data.

If N DL CCs are managed in a specific cell, a network may allocate M(M≤N) DL CCs to UE. In this case, the UE may monitor only the M limitedDL CCs and receive a DL signal. Furthermore, a network may give priorityto L (L≤M≤N) DL CCs and allocate major DL CCs to UE. In this case, theUE must monitor the L DL CCs. Such a method may be applied to uplinktransmission in the same manner.

A linkage between a carrier frequency (or DL CC) of a downlink resourceand a carrier frequency (or UL CC) of an uplink resource may beindicated by a higher layer message, such as an RRC message, or systeminformation. For example, a combination of DL resources and UL resourcesmay be configured by a linkage defined by System Information Block Type2(SIB2). Specifically, the linkage may mean a mapping relationshipbetween a DL CC in which a PDCCH carrying an UL grant is transmitted andan UL CC in which the UL grant is used and may mean a mappingrelationship between a DL CC (or UL CC) in which data for an HARQ istransmitted and an UL CC (or DL CC) in which an HARQ ACK/NACK signal istransmitted.

Cross-Carrier Scheduling

In a carrier aggregation system, there are two methods, that is, aself-scheduling method and a cross-carrier scheduling method form thepoint of view of scheduling for a carrier or a serving cell.Cross-carrier scheduling may also be called cross-component carrierscheduling or cross-cell scheduling.

Cross-carrier scheduling means that a PDCCH (DL grant) and a PDSCH aretransmitted in different DL CCs or that a PUSCH transmitted according toa PDCCH (UL grant) transmitted in a DL CC is transmitted through an ULCC different from an UL CC that is linked to the DL CC through which theUL grant has been received.

Whether cross-carrier scheduling will be performed may be activated ordeactivate in a UE-specific way, and each UE may be notified throughhigh layer signaling (e.g., RRC signaling) semi-statically.

If cross-carrier scheduling is activated, there is a need for a CarrierIndicator Field (CIF) providing notification that a PDSCH/PUSCHindicated by a PDCCH is transmitted through which DL/UL CC. For example,a PDCCH may allocate a PDSCH resource or PUSCH resource to any one of aplurality of component carriers using a CIF. That is, if a PDCCH on a DLCC allocates a PDSCH or PUSCH resource to one of multi-aggregated DL/ULCCs, a CIF is configured. In this case, a DCI format of LTE-A Release-8may be extended according to the CIF. In this case, the configured CIFmay be fixed to a 3-bit field, and the position of the configured CIFmay be fixed regardless of the size of the DCI format. Furthermore, aPDCCH structure (resource mapping based on the same coding and the sameCCE) of LTE-A Release-8 may be reused.

In contrast, if a PDCCH on a DL CC allocates a PDSCH resource on thesame DL CC or allocates a PUSCH resource on a single-linked UL CC, a CIFis not configured. In this case, the same PDCCH structure (resourcemapping based on the same coding and the same CCE) and DCI format asthose of LTE-A Release-8 may be used.

If cross-carrier scheduling is possible, UE needs to monitor a PDCCH fora plurality of pieces of DCI in the control region of a monitoring CCbased on a transmission mode and/or bandwidth corresponding to each CC.Accordingly, there is a need for the configuration of a search space andPDCCH monitoring capable of supporting such monitoring.

In a carrier aggregation system, a UE DL CC set is indicative of a setof DL CCs scheduled so that UE receives a PDSCH. A UE UL CC set isindicative of a set of UL CCs scheduled so that UE transmits a PUSCH.Furthermore, a PDCCH monitoring set is indicative of a set of one ormore DL CCs for performing PDCCH monitoring. A PDCCH monitoring set maybe the same as a UE DL CC set or may be a subset of a UE DL CC set. APDCCH monitoring set may include at least one of DL CCs within a UE DLCC set. Alternatively, a PDCCH monitoring set may be separately definedregardless of a UE DL CC set. DL CCs included in a PDCCH monitoring setmay be configured so that self-scheduling for a linked UL CC is alwayspossible. Such a UE DL CC set, UE UL CC set, and PDCCH monitoring setmay be configured in a UE-specific, UE group-specific, or cell-specificway.

If cross-carrier scheduling is deactivated, it means that a PDCCHmonitoring set is always the same as UE DL CC set. In this case, thereis no indication, such as separate signaling for a PDCCH monitoring set.However, if cross-carrier scheduling is activated, a PDCCH monitoringset may be defined in a UE DL CC set. That is, in order to schedule aPDSCH or PUSCH for UE, an eNB transmits a PDCCH through a PDCCHmonitoring set only.

FIG. 13 shows an example of the structure of a subframe according tocross-carrier scheduling in a wireless communication system to which anembodiment of the present invention may be applied.

FIG. 13 shows an example in which 3 DL CCs are aggregated in a DLsubframe for LTE-A UE and a DL CC “A” has been configured as a PDCCHmonitoring DL CC. IF a CIF is not used, each DL CC may send a PDCCH forscheduling its PDSCH without a CIF. In contrast, if a CIF is usedthrough higher layer signaling, only the single DL CC “A” may send itsPDSCH or a PDCCH for scheduling a PDSCH of a different CC using the CIF.In this case, the DL CCs “B” and “C” not configured as PDCCH monitoringDL CCs do not send a PDCCH.

D2D (Device-to-Device) Communication

Device-to-Device (D2D) communication technology refers to directcommunication between geographically adjacent UEs without going throughan infrastructure such as an eNB.

For D2D communication technology, commercially available technologiessuch as Wi-Fi direct and Bluetooth that mainly use an unlicensedfrequency band have been developed. However, the development andstandardization of D2D communication technologies using a licensedfrequency band are under way with the aim of improving the utilizationof cellular systems.

In general, D2D communication is limitedly used as a term indicative ofcommunication between things or thing intelligence communication. In anembodiment of the present invention, however, D2D communication mayinclude all types of communication between a variety of types of deviceshaving a communication function, such as smart phones and personalcomputers, in addition to simple devices having a communicationfunction.

FIG. 14 is a diagram conceptually illustrating D2D communication in awireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 14a shows an existing communication method based on an eNB. UE1 maysend data to an eNB in uplink, and the eNB may send data to UE2 indownlink. Such a communication method may be called an indirectcommunication method through an eNB. An Un link (i.e., a link betweeneNBs or a link between an eNB and a relay node, which may be called abackhaul link), that is, a link defined in an existing wirelesscommunication system, and/or an Uu link (i.e., a link between an eNB andUE or a link between a relay node and UE, which may be called an accesslink) may be related to the indirect communication method.

FIG. 14b shows a UE-to-UE communication method, that is, an example ofD2D communication. The exchange of data between UEs may be performedwithout the intervention of an eNB. Such a communication method may becalled a direct communication method between devices. The D2D directcommunication method has advantages of reduced latency and the use oflesser radio resources compared to the existing indirect communicationmethod through an eNB.

FIG. 15 shows an example of various scenarios of D2D communication towhich a method proposed in this specification may be applied.

A scenario for D2D communication may be basically divided into (1) anout-of-coverage network, (2) a partial-coverage network, and (3) anin-coverage network depending on where UE1 and UE2 are placed withincell coverage (i.e., in-coverage) and out of cell coverage (i.e.out-of-coverage).

The in-coverage network may be divided into an in-coverage-single-celland an in-coverage-multi-cell depending on the number of cellscorresponding to coverage of an eNB.

FIG. 15(a) shows an example of an out-of-coverage network scenario forD2D communication.

The out-of-coverage network scenario means that D2D communication isperformed between D2D UEs without control of an eNB.

From FIG. 15(a), it may be seen that only UE1 and UE2 are present andthe UE1 and the UE2 perform direct communication.

FIG. 15(b) shows an example of a partial-coverage network scenario forD2D communication.

The partial-coverage network scenario means that D2D communication isperformed between D2D UE placed within network coverage and D2D UEplaced out of the network coverage.

From FIG. 15(b), it may be seen that UE1 placed within network coverageand UE2 placed out of the network coverage perform communication.

FIG. 15(c) shows an example of an in-coverage-single-cell scenario, andFIG. 15(d) shows an example of an in-coverage-multi-cell scenario.

The in-coverage network scenario means that D2D UEs perform D2Dcommunication through control of an eNB within network coverage.

In FIG. 15(c), UE1 and UE2 are placed within the same network coverage(or cell) and perform D2D communication under the control of an eNB.

In FIG. 15(d), UE1 and UE2 are placed within network coverage, but areplaced within different network coverage. Furthermore, the UE1 and theUE2 perform D2D communication under the control of eNBs managing each ofnetwork coverage.

D2D communication is described in more detail below.

D2D communication may be performed in the scenarios of FIG. 15, but maybe commonly performed within network coverage (in-coverage) and out ofnetwork coverage (out-of-coverage). A link used for D2D communication(i.e., direct communication between UEs) may be called a D2D link, adirectlink, or a sidelink, but is hereinafter generally called asidelink, for convenience of description.

Sidelink transmission may be performed in an uplink spectrum in the caseof FDD and may be performed in an uplink (or downlink) subframe in thecase of TDD. Time Division Multiplexing (TDM) may be used for themultiplexing of sidelink transmission and uplink transmission.

Sidelink transmission and uplink transmission are not occurred at thesame time. Sidelink transmission is not occurred in a sidelink subframewhich partially or generally overlaps an uplink subframe or UpPTS usedfor uplink transmission. Furthermore, the transmission and reception ofa sidelink are also not occurred at the same time.

The structure of an uplink physical resource may be identically used asthe structure of a physical resource used for sidelink transmission.However, the last symbol of a sidelink subframe includes a guard periodand is not used for sidelink transmission.

A sidelink subframe may include an extended Cyclic Prefix (CP) or anormal CP.

D2D communication may be basically divided into discovery, directcommunication, and synchronization.

1) Discovery

D2D discovery may be applied within network coverage (including aninter-cell and an intra-cell). In inter-cell discovery, both synchronousand asynchronous cell deployments may be taken into consideration. D2Ddiscovery may be used for various commercial purposes, such asadvertising, issuing coupons, and finding friends, to UE within aproximity region.

If UE 1 has a role of sending a discovery message, the UE 1 sends adiscovery message, and UE 2 receives the discovery message. Thetransmission and reception roles of the UE 1 and the UE 2 may bechanged. Transmission from the UE 1 may be received by one or moreUE(s), such as the UE 2.

The discovery message may include a single MAC PDU. In this case, thesingle MAC PDU may include a UE ID and an application ID.

A physical sidelink discovery channel (PSDCH) may be defined as achannel for sending the discovery message. The structure of a PUSCH maybe reused as the structure of the PSDCH.

Two types Type 1 and Type 2 may be used as a resource allocation methodfor D2D discovery.

In the case of Type 1, an eNB may allocate a resource for sending adiscovery message in a non-UE-specific way.

To be specific, a radio resource pool comprising a plurality of subframesets and a plurality of resource block sets for transmitting andreceiving a discovery message within a specific period (in what follows,‘discovery period’) is allocated, and a discovery transmitting UEselects a specific resource within the radio resource pool in anarbitrary manner and transmits a discovery message.

The periodic discovery resource pool can be allocated for transmissionof a discovery signal in a semi-static manner. The configurationinformation of a discovery resource pool for discovery transmissionincludes a discovery period, a subframe set which can be used fortransmission of a discovery signal within the discovery period, andinformation about a resource block set. The configuration information ofthe discovery resource pool can be transmitted to the UE through upperlayer signaling. In the case of an in-coverage UE, the discoveryresource pool for discovery transmission is set up by an eNB and can beinformed to the UE through RRC signaling (for example, SystemInformation Block (SIB)).

The discovery resource pool allocated for discovery within one discoveryperiod can be multiplexed to a time-frequency resource block of the samesize through TDM and/or FDM scheme, where the time-frequency resourceblock of the same size can be called a ‘discovery resource’. A discoveryresource can be set as one subframe unit and include two PhysicalResource Blocks (PRBs) per slot in each subframe. One UE can use onediscovery resource for transmission of a discovery MAC PDU.

Also, a UE can transmit a discovery signal repeatedly within a discoveryperiod for transmission of one transport block. Transmission of a MACPDU by one UE can be repeated (for example, four times) contiguously ornon-contiguously within the discovery period (namely radio resourcepool). The transmission times of a discovery signal for one transmissionblock can be transmitted to the UE through upper layer signaling.

UE may randomly select a first discovery resource in a discoveryresource set which may be used for the repetitive transmission of an MACPDU and may determine the remaining discovery resources in relation tothe first discovery resource. For example, a specific pattern may bepreviously determined, and a next discovery resource may be determinedaccording to the predetermined specific pattern depending on theposition of a discovery resource first selected by UE. Alternatively, UEmay randomly select each discovery resource within a discovery resourceset which may be used for the repetitive transmission of an MAC PDU.

In the case of Type 2, a resource for discovery message transmission isallocated in a UE-specific way. Type 2 is subdivided into Type-2A andType-2B. Type-2A is a method of allocating, by an eNB, a resource at theinstance at which UE sends a discovery message within a discovery cycle,and Type-2B is a method of allocating resources semi-persistently.

In the case of Type-2B, RRC_CONNECTED UE requests an eNB to allocate aresource for the transmission of a D2D discovery message through RRCsignaling. Furthermore, the eNB may allocate the resource through RRCsignaling. When the UE transits to an RRC_IDLE state or when the eNBwithdraws resource allocation through RRC signaling, the UE releases themost recently allocated transmission resource. As described above, inthe case of Type-2B, a radio resource may be allocated through RRCsignaling, and the activation/deactivation of an allocated radioresource may be determined by a PDCCH.

A radio resource pool for receiving a discovery message may beconfigured by an eNB, and UE may be notified of the configured radioresource pool through RRC signaling (e.g., a System Information Block(SIB)).

Discovery message reception UE monitors both the aforementioneddiscovery resource pools of Type 1 and Type 2 in order to receive adiscovery message.

2) Direct Communication

The region to which D2D direct communication is applied includes anetwork coverage edge area (i.e., edge-of-coverage) in addition toinside and outside network coverage (i.e., in-coverage andout-of-coverage). D2D direct communication may be used for purposes,such as Public Safety (PS).

If UE 1 has a role of direct communication data transmission, the UE 1sends direct communication data, and UE 2 receives the directcommunication data. The transmission and reception roles of the UE 1 andthe UE 2 may be changed. The direct communication transmission from theUE 1 may be received by one or more UE(s), such as the UE 2.

D2D discovery and D2D communication may be independently defined withoutbeing associated with each other. That is, in groupcast and broadcastdirect communication, D2D discovery is not required. If D2D discoveryand D2D direct communication are independently defined as describedabove, UEs do not need to perceive adjacent UE. In other words, in thecase of groupcast and broadcast direct communication, all reception UEswithin a group are not required to be adjacent to each other.

A physical sidelink shared channel (PSSCH) may be defined as a channelfor sending D2D direct communication data. Furthermore, a physicalsidelink control channel (PSCCH) may be defined as a channel for sendingcontrol information (e.g., Scheduling Assignment (SA), a transmissionformat for direct communication data transmission, etc) for D2D directcommunication. The structure of a PUSCH may be reused as the structuresof the PSSCH and the PSCCH.

Two types of mode 1 and mode 2 may be used as a resource allocationmethod for D2D direct communication.

Mode 1 refers to a method of scheduling, by an eNB, data for D2D directcommunication by UE or a resource used for UE to send controlinformation. Mode 1 is applied to in-coverage.

An eNB configures a resource pool for D2D direct communication. In thiscase, the resource pool for D2D communication may be divided into acontrol information pool and a D2D data pool. When an eNB schedulescontrol information and a D2D data transmission resource within a poolconfigured for transmission D2D UE using a PDCCH or ePDCCH (enhancedPDCCH), the transmission D2D UE sends control information and D2D datausing the allocated resource.

Transmission UE requests a transmission resource from an eNB. The eNBschedules a resource for sending control information and D2D directcommunication data. That is, in the case of mode 1, the transmission UEneeds to be in the RRC_CONNECTED state in order to perform D2D directcommunication. The transmission UE sends a scheduling request to theeNB, and a Buffer Status Report (BSR) procedure is performed so that theeNB may determine the amount of resources requested by the transmissionUE.

Reception UEs monitors a control information pool. When decoding controlinformation related to reception UE, the reception UE may selectivelydecode D2D data transmission related to corresponding controlinformation. The reception UE may not decode a D2D data pool based on aresult of the decoding of the control information.

Mode 2 refers to a method of randomly selecting, by UE, a specificresource in a resource pool in order to send data or control informationfor D2D direct communication. Mode 2 is applied to out-of-coverageand/or edge-of-coverage.

In mode 2, a resource pool for sending control information and/or aresource pool for sending D2D direct communication data may bepre-configured or may be configured semi-statically. UE is supplied witha configured resource pool (time and frequency) and selects a resourcefor D2D communication transmission in the resource pool. That is, the UEmay select a resource for control information transmission in a controlinformation resource pool in order to send control information.Furthermore, the UE may select a resource in a data resource pool inorder to send D2D direct communication data.

In D2D broadcast communication, control information is transmitted bybroadcasting UE. Control information is explicitly and/or implicitlyindicative of the position of a resource for data reception in relationto a physical channel (i.e., a PSSCH) on which D2D direct communicationdata is carried.

3) Synchronization

A D2D Synchronization Signal/sequence (D2DSS) can be used by a UE toobtain time-frequency synchronization. In particular, since the eNB isunable to control a UE located beyond network coverage, a new signal andprocedure can be defined to establish synchronization among UEs. A D2Dsynchronization signal can be called a sidelink synchronization signal.

A UE transmitting a D2D synchronization signal periodically can becalled a D2D synchronization source or a sidelink synchronizationsource. In case a D2D synchronization source is an eNB, the structure ofa D2D synchronization signal being transmitted can be identical to thatof PSS/SSS. In case the D2D synchronization source is not an eNB (forexample, a UE or GNSS (Global Navigation Satellite System)), thestructure of a D2D synchronization signal being transmitted can be newlydefined.

The D2D synchronization signal is transmitted periodically with a periodnot shorter than 40 ms. Each UE can have a physical-layer D2Dsynchronization identity. The physical-layer D2D synchronizationidentifier may be called a physical-layer sidelink synchronizationidentity or simply a D2D synchronization identifier.

The D2D synchronization signal includes a D2D primary synchronizationsignal/sequence and a D2D secondary synchronization signal/sequence.These signals can be called a primary sidelink synchronization signaland a secondary sidelink synchronization signal, respectively.

Before transmitting a D2D synchronization signal, the UE may firstsearch for a D2D synchronization source. If a D2D synchronization sourceis found, the UE can obtain time-frequency synchronization through a D2Dsynchronization signal received from the D2D synchronization sourcefound. And the corresponding UE can transmit the D2D synchronizationsignal.

Moreover, a channel for transmitting necessary information to be usedfor device-to-device communication as well as for synchronization may berequired, and a channel for this purpose may be defined. Such a channelmay be referred to as PD2DSCH (Physical D2D Synchronization Channel) orPSBCH (Physical Sidelink Broadcast Channel.

In D2D communication, direct communication between two devices isdescribed below as an example, for clarity, but the scope of the presentinvention is not limited thereto. The same principle described in anembodiment of the present invention may be applied to D2D communicationbetween a plurality of two or more devices.

Hereinafter, methods for transmitting D2D control information or D2Ddata or both, which are proposed according to embodiments of the presentinvention, are described in detail.

As described above, D2D link may be represented as a sidelink

Furthermore, D2D control information may be represented as SidelinkControl Information (SCI), and the D2D control information may betransmitted and received through a physical sidelink control channel(PSCCH).

Furthermore, D2D data may be transmitted and received through a physicalsidelink shared channel (PSSCH), and the transmission/reception of theD2D data may be represented as the transmission and reception of PSSCHs.

In performing D2D communication, D2D control information may be definedin order for D2D UE to demodulate D2D data.

As described above, the D2D control information may be represented asSCI, and the D2D control information and the SCI are interchangeablyused hereinafter.

In this case, the D2D control information may be transmitted through achannel (or as a separate signal) separate from a D2D communicationchannel through which the D2D data is delivered

As described above, the D2D communication channel may be represented asa PSSCH, and the D2D communication channel and the PSSCH areinterchangeably used hereinafter.

Furthermore, methods to be described hereinafter may be identicallyapplied when control information required to deliver a D2D discoverymessage is separately transmitted.

The D2D control information may include some of or the entireinformation, such as a New Data Indicator (NDI), Resource Allocation(RA) (or a resource configuration), a Modulation and Coding Scheme/Set(MCS), a Redundancy Version (RV), and a Tx UE ID.

The D2D control information may have a different combination of piecesof information depending on a scenario to which the D2D communication isapplied.

In general, control information (CI) may be decoded prior to a datachannel because it is used to demodulate the data channel.

Accordingly, pieces of UE that receive the control information may needto be aware the location of time and frequency resources through whichthe control information is transmitted and related parameters for thedemodulation of the data channel.

For example, in an LTE (-A) system, in the case of a PDCCH, a UEID-based hashing function is used by a transmission stage (e.g., an eNB)and a reception stage (e.g., UE) in common so that the UE can be awarethat the PDCCH will be transmitted at a specific location of specificsymbols of each subframe.

Furthermore, in an LTE (-A) system, in the case of a BCH, an eNB and UEshare information, indicating that system information is delivered in aspecific symbol of a specific subframe (SF) in a cycle of 40 ms, inadvance.

As described above, in order for UE to properly obtain the controlinformation, demodulation-related information (or parameter) of thecontrol information may need to be sufficiently delivered to the UE inadvance.

Likewise, in a system supporting D2D communication, in order for D2D UEto successfully demodulate D2D control information, a parameter relatedto the transmission of the D2D control information may need to be sharedby the D2D UE in advance.

The parameter related to the transmission of the D2D control informationmay include, for example, a subframe/slot index, a symbol index, or anRB index.

Furthermore, the parameter related to the transmission of the D2Dcontrol information may be the DCI of a specific format and may beobtained through a PDCCH from an eNB or another D2D UE.

The DCI of the specific format means a newly defined DCI format and maybe, for example, a DCI format 5.

In an embodiment, the D2D control information may be designated to betransmitted in all of subframes designated as D2D subframes (i.e.,subframes designated for D2D transmission), a series of subframes (a setof subframes or a subframe set) that belong to all the subframes andthat has a specific index, or a subframe set having a specific cycle.

Such potential transmission subframe or subframe set of the D2D controlinformation may be recognized by UE in advance through (higher layer)signaling or based on UE-specific information (e.g., a UE ID) in such amanner that the UE may autonomously calculate the transmission subframeor subframe set.

Furthermore, a resource region in which a D2D data channel is deliveredand a resource region in which D2D control information is delivered maybe differently configured in a time domain.

That is, the D2D control information may be defined to be transmitted ina designated time unit, that is, periodically (or while hopping in adesignated time-frequency domain pattern). The D2D data channel may bedefined to be delivered only in a resource region indicated by the D2Dcontrol information.

Unlike a method for transmitting D2D control information and D2D datatogether, the method means a method in which a case where the D2Dcontrol information is transmitted and a case where D2D data istransmitted are independently operated.

Specifically, if the D2D control information and the D2D data areseparately transmitted, (1) parameters (e.g., scrambling, CRC, CRCmasking, or demodulation sequence generation parameters) applied to theD2D control information and the D2D data are independently set or (2) aparameter applied to the D2D data is indicated through the D2D controlinformation.

In the case of (2), D2D UE attempts (e.g., explicit or blind decoding)monitoring and decoding at the D2D control information using a potentialparameter in a (potential) resource (i.e., subframe or subframe set) inwhich the D2D control information is reserved to be transmitted and doesnot perform decoding attempts at the D2D control information in aresource region other than the potential resource.

In this case, there is an advantage in that power consumption of UE canbe reduced.

Furthermore, if UE demodulates D2D data, the UE has only to demodulateonly designated information at a designated point using a parameter andD2D data resource region information obtained through the D2D controlinformation. Accordingly, there is an advantage in that powerconsumption of UE can be reduced.

In an embodiment for implementing the aforementioned methods, a methodfor performing, by pieces of UE, blind search (or decoding) on aspecific resource region in order to obtain D2D control information at aspecific point of time and decoding D2D control information matched witheach of the pieces of UE is described below.

In this case, whether D2D control information is matched with each ofthe pieces of UE may be implemented based on UE-specific information orUE group-specific (UE group-common) information.

That is, only corresponding UE may perform (blind) decoding on D2Dcontrol information by applying UE-specific scrambling or CRC masking tothe D2D control information, or all of a plurality of pieces of UE (or agroup or all) may decode the D2D control information by applyingUE-group common scrambling or CRC masking to the D2D controlinformation.

Accordingly, UE or a UE group may obtain information related to D2D datademodulation from D2D control information that has been successfullydecoded.

The D2D control information (or SCI) includes a parameter (in this case,including a parameter obtained through blind search from a given D2Dcontrol channel set in addition to a predetermined parameter) used in aD2D control channel (PSCCH) in addition to explicit information includedin D2D control information.

The parameter used in the D2D control channel may include scrambling,CRC masking, use resource information, and reference signal relatedparameters.

Accordingly, UE may not perform blind decoding on D2D data.

In other words, UE or a UE group performs blind decoding on D2D controlinformation through a specific parameter at a specific point of timeusing its own unique information or based on previously (higher-layer)signaled information in order to obtain the D2D control information.

Through such blind decoding, the UE or UE group may obtain bothscheduling information related to data demodulation and variousparameters used to generate and transmit a D2D control channel (orcontrol information).

Accordingly, the UE or UE group uses the parameter related to the D2Dcontrol channel and the decoded scheduling information to decode anddemodulate a D2D data channel.

In this case, the D2D data channel may be represented as a physicalsidelink shared channel (PSSCH).

The scheduling information may refer to explicit information, such asresource allocation information, an NDI, an MCS, or a Tx UE ID requiredto demodulate D2 data.

Furthermore, as described above the scheduling information may berepresented as Sidelink Control Information (SCI).

UE is not required to perform parameter blind search, such as thatperformed on a D2D control channel (or a PSCCH) with respect to a D2Ddata channel (PSSCH), because it uses a parameter through blind searchwith respect to the D2D control channel without any change or uses a newparameter generated based on the parameter to generate the D2D datachannel.

In another embodiment, a D2D control channel and a D2D data channel maybe transmitted in the same subframe (from the standpoint of UE or a UEgroup) or may be implemented to have different cycles in time.

That is, such a method is a method for performing, by UE, blind decodingon a D2D control channel in a specific subframe and demodulating the D2Ddata of the same subframe based on corresponding information.

In this case, it is assumed that the UE will not perform blind decodingon the D2D data.

Instead, the UE may perform blind decoding on only the D2D controlchannel so that blind decoding complexity is dependent on only a D2Dcontrol channel in a corresponding subframe.

That is, the UE performs blind decoding on only D2D control informationin the corresponding subframe.

If UE has to perform blind decoding on D2D data, when D2D controlinformation and D2D data are transmitted in the same subframe, a problemin that the UE′ blind decoding trials suddenly increases may begenerated.

In this case, the number of pieces of UE capable of detecting D2Dcontrol information through blind decoding in a specific subframe may belimited.

That is, if the transmission periods of D2D control information and D2Ddata are fixed, there may be a case where the D2D control informationand the D2D data are transmitted in the same subframe in some situationsdepending on their cycles.

In this case, if there is a limit to blind decoding trials in acorresponding subframe, the blind decoding trials of a D2D controlinformation channel or a D2D data channel or both may be reduced.

In order to reduce such a problem, the blind decoding of UE may beintroduced only in a D2D control channel so as to prevent a limitationto blind decoding trials attributable to a variation of blind decodingcomplexity.

Furthermore, there is an advantage that the degree of freedom ofscheduling for a D2D data channel may be increased by introducing blinddecoding in only a D2D control channel.

That is, although D2D control information and D2D data are placed in thesame subframe, if blind decoding is applied to a D2D control channelonly, there is no limitation to blind decoding complexity.

Accordingly, although a D2D control channel is periodically transmittedin a specific subframe, a subframe for transmitting a D2D data channelmay be determined and allocated even without avoiding a subframe inwhich the D2D control channel is transmitted.

Assuming that a D2D control channel is detected once and thentransmitted in a specific subframe after D2D data associated with theD2D control channel is transmitted, D2D control information does notneed to be transmitted again in the transmission opportunity subframe(i.e., a D2D control channel transmission period or PSCCH period) of theD2D control channel during a time interval until a subframe in which theD2D data will be transmitted.

Likewise, from the standpoint of UE, blind decoding (or monitoring) maynot be performed on a D2D control channel until a D2D data subframeindicated by D2D control information after blind decoding is performedon the D2D control channel.

In this case, power consumption of the UE can be reduced. This may bedifferently configured for each piece of UE.

If the period in which a D2D control channel is transmitted (or a PSCCHperiod) and a subframe offset are differently configured in each ofpieces of UE, each of the pieces of UE may be aware of a subframe inwhich monitoring for D2D control information needs not to be performed.

That is, when each of pieces of UE performs blind decoding on D2Dcontrol information in a specific subframe, it may be aware how long itmay perform discontinuous reception (DRX) or discontinuous transmission(DTX) by taking into consideration the monitoring subframe period andoffset of its own D2D control information.

After receiving and demodulating D2D control information (i.e.scheduling allocation), UE may calculate how long it does not need tomonitor D2D control information, that is, it may perform DTX, properlyusing a specific bit value and D2D control information subframe period(i.e., PSCCH period) information carried on corresponding subframeindex, UE ID, or D2D control information.

FIG. 16 is a diagram showing an example of a method for transmitting andreceiving D2D control information and D2D data, which is proposedaccording to an embodiment of the present invention.

In FIG. 16, a C1 1601 is indicative of a resource that belongs to D2Dresources allocated to UE 1 (or a UE-group 1) and that is used totransmit D2D control information.

The C1 1601 may be obtained through an (E-)PDCCH, an SIB,“preconfigured”, or “relaying by UE.”

For example, UE may obtain the C1 (or the SCI format 0) through the DCIformat 5 transmitted through a PDCCH.

Furthermore, the period of the C1 corresponds to a period #1.

A C2 1602 is indicative of a resource that belongs to D2D resourcesallocated to UE 2 (or a UE-group 2) and that is used to transmit D2Dcontrol information.

The period of the C2 corresponds to a period #2.

The periods of the C1 and C2 may be represented as a PSCCH period #1 anda PSCCH period #2, respectively.

In FIG. 16, the first C1 information indicates a parameter related tothe transmission of D2D data #1 1603 and indicates various types ofinformation (e.g., scheduling information, such as a DM RS sequence, anMCS, and RA) for reception UE in order to demodulate the D2D data #1.

Furthermore, the first C2 information indicates a parameter related tothe transmission of D2D data #2 1604 and indicates various types ofinformation (e.g., scheduling information) for reception UE in order todemodulate the D2D data #2.

In FIG. 16, second C1 information 1605 and second C2 information 1086indicate parameters (e.g., scheduling information) following the firstD2D data #1 1603 and the first D2D data #2 1604, that is, parametersassociated with second Data #1 and Data #2 1607.

Each of pieces of UE performs blind decoding on D2D control information,corresponding to each of pieces of UE, with respect to a correspondingsubframe because it is previously aware of the location of a subframefor D2D control information where the UE may perform monitoring.

FIG. 17 is a diagram showing another example of a method fortransmitting and receiving D2D control information and D2D data, whichis proposed according to an embodiment of the present invention.

In FIG. 17, UE may be aware that D2D data (D2D data #1) related to a C11701 is delivered in a D2D data #1 subframe 1702 by performing blinddecoding on the C1 1701.

Furthermore, if the UE is previously aware that there is no C1 in asubframe 1703 periodically reserved (or allocated) for the purpose oftransmitting D2D control information after the C1, the UE may skip thereserved subframe 1703 without performing monitoring or blind decoding.

That is, FIG. 17 shows that UE does not perform additional monitoringand blind decoding on D2D control information in a periodically reservedsubframe present between the C1 and the data #1.

In this case, it may be considered that the UE performs a DTX operationin a specific subframe in order to reduce power consumption because itmay be previously aware that it does not need to perform monitoring andblind decoding on D2D control information in the specific subframe.

FIG. 18 is a diagram showing yet another example of a method fortransmitting and receiving D2D control information and D2D data, whichis proposed according to an embodiment of the present invention.

In the example of FIG. 17, UE has skipped blind decoding for all ofsubframes periodically reserved between the C1 and the data #1.

In contrast, FIG. 18 shows a method for skipping, by UE, a reserved D2Dcontrol information subframe from a monitoring subframe only when apreviously agreed condition is satisfied without skipping blind decodingfor all of reserved D2D control information subframes, if a D2D controlinformation subframe reserved to transmit D2D control information ispresent between the D2D control information and a D2D data subframeindicated by the D2D control information.

From FIG. 18, it may be seen that UE performs blind decoding in a C111801 and a C13 1803 and skips blind decoding in a C12 1802.

That is, all of the monitoring subframes C11, C12, and C13 of candidateD2D control information between the C11 1801 and data #11 1804 are notskipped.

For example, the UE performs monitoring on the last subframe C13 1803 ofthe candidate subframes present between the C11 1801 and the data #111804 for blind decoding.

In some embodiments, if N D2D control information candidate subframesare present between a D2D control information (or schedulinginformation) subframe and a D2D data transmission subframe, blinddecoding for K candidate subframes placed at the last portion may beskipped.

In this case, the value “k” may be set depending on a system operation.

In some embodiments, if a D2D control information subframe is dividedinto a subframe used for D2D transmission and a subframe used for D2Dreception (i.e., if two types of subframes are present because theycannot be transmitted and received at the same time due to a half-duplexconstraint), the blind decoding skip rule may be applied to only thesubframe used for D2D transmission.

If there is no distinction between a subframe used for D2D transmissionand a subframe used for D2D reception, the blind decoding skip rule maybe applied by taking into consideration both the two types (D2Dtransmission and D2D reception) of subframes.

In some embodiments, if the valid period of D2D control information ispresent, assuming that additional D2D control information does notarrive during the valid period, UE may neglect D2D control informationthat arrives between a D2D control information subframe and a D2D datasubframe, that is, may apply the blind decoding skip rule.

Furthermore, assuming that D2D control information subframes are used bya plurality of pieces of UE, each of the pieces of UE may calculate asubframe that belongs to the D2D control information subframes and thatmay be monitored using its own ID or another parameter, such as a D2Dsubframe index.

In this case, a method for calculating, by each of pieces of UE, its ownD2D control information subframe may be performed like a method forcalculating a paging subframe that may be monitored by the UE, that is,calculating the index of a subframe that must be received by the UEafter waking up from sleep mode using a UE ID and another parameter.

FIG. 19 is a diagram showing an example of a method for configuring D2Dcontrol information depending on D2D transmission mode, which isproposed according to an embodiment of the present invention.

FIG. 19 shows that some of resources allocated using each of two D2Dresource allocation methods, that is, two types of transmission mode(transmission mode 1 and transmission mode 2), are configured as commonresources if the two D2D resource allocation methods are used.

FIG. 19a shows the resource allocation of D2D control information in anin-coverage scenario, that is, transmission mode 1, and FIG. 19b showsthe resource allocation of D2D control information in a partial orout-coverage scenario, that is, transmission mode 2.

The resource of control information in transmission mode 1 is indicatedby C1 or C2, and the resource of control information in transmissionmode 2 is indicated by P or S.

From FIG. 19, it may be seen that the resources C1 and P have beenconfigured to be aligned in the same time resource or the same frequencyresource or both.

That is, FIG. 19 shows that the resources C1 and P have been configuredas common resources (e.g., cell-specific or UE group-specific).

In the resource configurations of FIG. 19, if UE changes a resourceallocation method, it may use the common resource subframe as a fallbacksubframe in which a D2D control channel may be monitored.

That is, common resources configured using different resource allocationmethods may mean candidate subframes in which UE is obliged to monitorD2D control information when mode of a resource allocation methodswitches.

Accordingly, pieces of UE to which resources have been allocatedaccording to transmission mode 1 or pieces of UE to which resources havebeen allocated according to transmission mode 2 may need to performblind decoding on the resource P or C1 corresponding to commonresources.

In this case, pieces of UE within a cell may have different resourceallocation methods, that is, different types of transmission mode.Resources may be configured so that one piece of UE has the two types oftransmission mode.

Transmission mode 1 and transmission mode 2 do not mean only a resourceallocation method for D2D communication, but may be concepts indicativeof a resource allocation method for D2D discovery.

That is, from the standpoint of a piece of UE, a D2D discovery resourcemay be set as transmission mode 1 and a D2D communication resource maybe set as transmission mode 2, and vice versa.

From the standpoint of a plurality of pieces of UE, transmission mode 1,transmission mode 2, D2D discovery, and D2D communication combinationsmay be configured in various ways.

In this case, previously designated UE (e.g., a UE group, all of typesof UE within a cell, or all of types of D2D-enabled UE) may be definedto monitor a common resource set by defining the concept of a defaultresource set or common resource set in transmission mode 1 ortransmission mode 2.

Timing relations between a Scheduling Grant (SG) (or DCI), SchedulingAssignment (SA), and D2D data transmission in D2D communication, whichare proposed according to an embodiment of the present invention, aredescribed in detail below.

A Scheduling Grant (SG) used hereinafter is indicative of DownlinkControl Information (DCI) transmitted from an eNB to D2D UE and may meana parameter related to D2D communication.

The scheduling grant may be transmitted in a PDCCH/EPDCCH and may berepresented as a DCI format 5.

Furthermore, the Scheduling Assignment (SA) may be indicative of D2Dcontrol information and may mean control information transmitted andreceived between pieces of D2D UE, including resource allocationinformation for the transmission and reception of D2D data.

The Scheduling Assignment (SA) may be transmitted through a PSCCH andmay be represented as an SCI format 0.

First, contents related to a method for notifying UE of a resource usedfor D2D data transmission and a resource used for Scheduling Assignment(SA) transmission for transmitting D2D data transmission-relatedscheduling information are described with reference to Table 5 below.

Furthermore, a method described with reference to Table 3 is only anembodiment, and D2D data transmission and SA transmission may beperformed using methods other than the method of Table 5.

TABLE 5 Signaling methods Resource (or resource pool) indication methods(to be used for the following transmission) Being transmitted ResourceFor Scheduling For Data Allocation Scenarios Assignment communicationMode 1 In- SIB (or (E)PDCCH) SIB (or (E)PDCCH) (eNB coverage (This maybe (This may be schedules) triggered by a D2D triggered by a D2Dscheduling request scheduling request (D-SR)) (D-SR)) Edge-of- Via otherVia other coverage forwarding UE(s) forwarding UE(s) SIB or other SIB orother sig. forwarding sig. forwarding Out- Pre-configured orPre-configured or overage other other A semi-static resource poolrestricting the available resources for data or control or both may beneeded D2D communication capable UE shall support at least Mode 1 forin-coverage Mode 2 In- SIB (or (E)PDCCH) SIB (or (E)PDCCH) (UE coverageselects) Edge-of- Via other Via other coverage forwarding UE(s)forwarding UE(s) SIB or other SIB or other sig. forwarding sig.forwarding Out- Pre-configured or Pre-configured or coverage other otherThe resource pools for data and control may be the same A semi-staticand/or pre-configured resource pool restricting the available resourcesfor data or control or both may be needed D2D communication-capable UEshall support Mode 2 for at least edge-of-coverage and/orout-of-coverage

In Table 5, Mode 1 and Mode 2 in a D2D resource allocation method may bedivided as follows.

From a transmitting UE perspective, UE may operate in the two types ofmode for resource allocation:

Mode 1: an eNodeB or rel-10 relay node schedules exact resources used byUE to transmit direct data and direct control information

Mode 2: UE on its own selects resources from resource pools to transmitdirect data and direct control information

Referring to Table 5, resource allocation used for SA transmission andD2D data to transmission in Mode 1 and Mode 2 may be implemented throughan SIB in the case of the in-coverage scenario. That is, an eNB maynotify UE of resource allocation for SA transmission and D2D datatransmission through an SIB.

In some embodiments, scheduling allocation may be performed and dataresources may be allocated using the dynamic control signal (e.g., aPDCCH, an EPDCCH, or a MAC CE) of an eNB.

In some embodiments, resource pools may be previously allocated throughan SIB, and UE may be notified of (time-frequency resources) detailedresource allocation information (SA resources and D2D data resources)through a dynamic control signal within the allocated resource range.

In this case, the SA for direct communication may deliver the detailedresource allocation information (e.g., using relative locationinformation or offset information) used in direct data communication.

That is, UE may receive SA and data resource pools through an SIB andmay receive detailed SA and data transmission resources through the SA.

If a plurality of resource pools has been previously allocated to UE, SAmay be used to indicate one or some of the allocated resource pools.

In Table 3, in the case of the out-coverage scenario, UE may be aware ofSA resource pools and data resource pools based on resourceconfiguration information that has been pre-configured or received fromcoverage UE.

In this case, if the UE has to determine detailed resources for SAtransmission and D2D data transmission, it may autonomously select SAresources.

Thereafter, the UE may include resources allocated in relation to D2Ddata transmission in SA contents and transmit the SA contents to D2Dreception UE so that the D2D reception UE is aware of a resource regionin which D2D data is received.

In this case, in order to reduce information included in the SAcontents, resource region information (e.g., time and frequency index)in which SA has been detected may be used as part of D2D data resourceallocation information.

That is, the final resource region is calculated using both the SAresource-related information and the SA contents information.

For example, an SA (transmission) resource-related parameter may be usedto obtain only time domain information (e.g., a time domain parameterand a subframe index) of a D2D data resource region, and informationdelivered in SA may be used to provide notification of frequency domaininformation (e.g., a frequency domain parameter and an RB index).

In some embodiments, the SA resource-related parameter may be used todesignate the absolute locations (e.g., time and frequency indices) ofD2D data resources, and resource allocation information included in SAcontents may be used to provide notification of the relative locationsof D2D data resources.

In some embodiments, the SA (transmission) resource-related parametermay be used to provide notification of a random back-off or transmissionprobability value.

Furthermore, signaling contents transmitted from an eNB to D2Dtransmission UE may include a resource configuration, an MCS, etc. fordirect scheduling allocation.

The signaling contents may be represented as Downlink ControlInformation (DCI) or a Scheduling Grant (SG).

The timing relation between an eNB-dynamic control signal and an SAtransmission time is described in detail below.

If a D2D resource pool is allocated through a System Information Block(SIB) and UE autonomously determines SA resources and resources for D2Ddata transmission based on the allocated D2D resource pool, aneNB-dynamic control signal, such as a PDCCH/EPDCCH, may not be required.

In a situation in which all resources are managed by an eNB as in thein-coverage scenario, however, if an eNB controls D2D SA and resourceallocation for direct data in real time, the utilization of theresources may become further efficient. In this case, an eNB-dynamiccontrol signal is necessary.

Accordingly, a method using an eNB-dynamic control signal (e.g., ascheduling grant or an MAC CE using DCI) and when D2D transmission UEthat has received an eNB-dynamic control signal (i.e., an eNB schedulinggrant for SA and/or data for D2D) will transmit SA to D2D reception UEneed to be clearly defined.

As described above, an eNB may transmit an SG to D2D UE for (1)scheduling to regarding SA transmission and (2) scheduling regardingdata transmission.

In this case, the scheduling may mean scheduling related to D2Dtransmission, and scheduling information may include resource allocationinformation, an MCS, an RV, and an NDI.

In some embodiments, an eNB may transmit a single SG to D2D UE in orderto indicate whether it is scheduling regarding SA transmission orscheduling regarding D2D data transmission.

In this case, an implement may be possible so that an implicitassociation between SA and data is formed and D2D UE is capable ofestimating each of pieces of (SA, data) scheduled information.

For example, D2D UE may receive an SG related to SA transmission from aneNB and check the location or approximate location of D2D datatransmission resources having linkage to the SA (or the same is true ofscheduling information).

In some embodiments, D2D UE may receive an SG related to datatransmission from an eNB and check a resource location and relationinformation related to SA transmission having linkage to data.

A method 1 to a method 4 below shows timing relations between a dynamiccontrol signal transmitted from an eNB to D2D transmission UE and SAtransmitted from D2D transmission UE to D2D reception UE.

That is, the timing relation between the reception of a Scheduling Grant(DCI) from an eNB and the transmission of Scheduling Assignment (SA) ordata or both from D2D transmission UE to D2D reception UE is describedin detail below in connection with the method 1 to the method 4.

Method 1

FIG. 20 is a diagram illustrating an example of the timing relationshipbetween SG reception and SA transmission in a D2D UE proposed in thisspecification.

FIG. 20 shows that, if D2D SA (scheduling assignment) SFs (subframes)2001 and 2002 are periodically configured, when a D2D transmission UEreceives a scheduling grant (SG) from an eNB during the D2D SA SF period(or PSCCH period) (S2010), the D2D transmission UE transmits ascheduling assignment in the first D2D SA SF 2002 that comes after thereceived SG SF (S2020).

Method 2

FIGS. 21 and 22 are a flowchart illustrating an example of the timingrelation between SG reception and SA transmission in D2D UE, which isproposed according to an embodiment of the present invention.

FIG. 21 shows a method for transmitting, by D2D transmission UE, SA toD2D reception UE by taking into consideration the processing time of UE(or a system) after receiving an SG from an eNB.

That is, the D2D transmission UE receives SG from the eNB, configures anSA based on the received SG, and transmits the SA to the D2D receptionUE by taking into consideration the time taken to transmit the SA, thatis, processing delay.

In this case, if the processing delay is taken into consideration, theSA transmission of the D2D transmission UE may be performed in a fourthsubframe #n+4 after an SG subframe (subframe #n) received from the eNB.

That is, when D2D transmission UE receives an SG in a subframe #n atstep S2101, it may transmit SA to D2D reception UE in a fourth subframe#n+4 2101 at step S2102.

In this case, if the fourth subframe #n+4 2201 is not a D2D SA subframe,the D2D transmission UE may transmit the SG in a D2D SA subframe 2202that first arrives after the fourth subframe #n+4.

In contrast, if the D2D transmission UE receives the SG from the eNB inthe subframe #n and a D2D SA SF that first arrives subsequently ispresent in the fourth subframe #n+4, the D2D transmission UE determinesthat the D2D SA SF is not valid or available.

Accordingly, the D2D transmission UE transmits the D2D SA in asubsequent (or next period) available D2D SA SF.

The n+4 is an embodiment and may be generalized as “n+k”, that is, D2DSA is transmitted in a k-th SA SF after the SG is received.

The value “k” may be configured by taking into consideration thedevelopment of the future technology, performance of UE and so on.

Furthermore, the value “k” may be differently configured for each pieceof UE depending on the capability of the UE.

FIG. 21 shows an example of a method for transmitting SA in a subframe#n+k, and FIG. 22 shows an example of a method for transmitting SA in anSA SF that is first reaches after a subframe #n+k.

In relation to the configuration of the value “k”, it is different froman LTE (-A) system in that resources are not explicitly allocated, but aD2D resource pool is determined. In this case, resources are selectedand transmitted, and different values are configured between pieces ofUE if a collision between resources is permitted.

The method of FIGS. 21 and 22 may be identically applied to D2D datatransmission.

That is, when D2D UE receives control information (or schedulinginformation) related to D2D data transmission from an eNB in a subframen, the D2D UE may transmit D2D data in a subframe n+k′ by taking intoconsideration the processing time of the D2D UE.

The control information related to the D2D data transmission may be anSG or SA related to the resource allocation of the D2D datatransmission.

The k′ value may be configured differently from a value “k” at an SAtransmission time point.

In general, a k′> (or =) k relation may be established by taking intoconsideration a probability that D2D data transmission may occur a bitlater.

Method 3

An operation when SA SFs are configured as a group, that is, a pluralityof SFs is allocated for SA and operated, is described below.

FIG. 23 is a diagram showing another example of the timing relationbetween SG reception and SA transmission in D2D UE, which are proposedaccording to an embodiment of the present invention.

FIG. 23 shows a method for transmitting, by D2D transmission UE, SA toD2D reception UE in the first SA SF after a subframe n+4 when itreceives an SG (or resource allocation DCI) from an eNB in a subframe SF#n.

In this case, if the first SA SF after the subframe n+4 is a group of Mcontiguous SA SFs, when the D2D transmission UE receives the SG in thesubframe SF #n at step S2310, it transmits the SA in the SA SF groupthat is first met after the subframe n+4 at step S2330.

What the SA will be transmitted in which one of the M SFs of the SA SFgroup may be finally aware through the SG at step S2320.

Furthermore, if an SA or data transmission subframe (SF) includes aplurality of subframes, a specific bit (or specific field) of a DCIformat may be used to determine the location of the SA or datatransmission subframe.

For example, a bit to determine the DCI formats 0/1, a hopping bit, orsome of or all of RA bits may be used to determine the location of theSA or data transmission subframe.

Furthermore, the SG may be divided for SA and data purposes and may befurther divided for special purposes, if necessary.

Accordingly, a bit to determine the DCI formats 0/1, a hopping bit, orsome of or all of RA bits may be used to divide the purposes of an SG.

Method 4

A method for providing notification of the location of an SA SF throughRadio Resource Control (RRC) is described below.

FIG. 24 is a diagram showing yet another example of the timing relationbetween SG reception and SA transmission in D2D UE, which is proposedaccording to an embodiment of the present invention.

FIG. 24 shows a method of previously providing notification of thelocation of an SA SF through RRC at step S2410 and simply using an SG(e.g., PDCCH DCI) as an activation purpose in which the SA SF may beused at step S2420.

In this case, a special index may be defined so that an associationbetween RRC signaling and activation DCI may be checked.

That is, DCI indicative of the activation of an SA SF may be defined todenote the RRC of which index.

DCI, that is, an SG, accurately indicates the activation of an SA SF orSF set transmitted through RRC. In this case, an RRC set including aseries of indices mapped to the DCI may be previously designated.

Furthermore, D2D transmission UE transmits SA to D2D reception UEthrough the SA SF whose activation has been indicated by the SG at stepS2430.

A method for providing notification of the time location of SA resourcesor D2D data resources or both through the RRC signaling of FIG. 24 isdescribed in detail later.

The timing relation between SA transmission and D2D data transmission inD2D UE, which is proposed according to an embodiment of the presentinvention, is described in detail below with reference to FIGS. 26 to28.

FIG. 25 is a diagram showing an example of the timing relation betweenD2D SA transmission and D2D data transmission, which is proposedaccording to an embodiment of the present invention.

Regarding the timing between a D2D SA SF and a D2D data SF, D2D data maybe implicitly transmitted and received according to a predeterminedrule.

FIG. 25 shows a method for transmitting, by D2D transmission UE, SA toD2D reception UE in a subframe #n at step S2510 and transmitting D2Ddata to the D2D reception UE in an available D2D data SF 2501 that firstarrives after a subframe “n+k” at step S2520, as in the timing relationbetween SG transmission and SA transmission.

Likewise, the value “k” is configurable and a different value “k” may beconfigured for each piece of UE.

Furthermore, as in the timing relation between SG transmission and SAtransmission, UE may be notified of an available D2D data SF group, anda specific SF (e.g., a subframe #m) within the D2D data SF group may beseparately indicated.

In this case, a parameter “k” indicative of the specific SF may beincluded in SA contents.

The value “k” of the indication parameter may be differently interpreteddepending on the following conditions.

That is, the value “k” of the indication parameter may be differentlyinterpreted depending on each pieces of UE, the location of a resourceregion, a UE group or the scenario (i.e., in-coverage, out-coverage, andedge-of-coverage) or both.

FIG. 26 is a diagram showing another example of the timing relationbetween D2D SA transmission and D2D data transmission, which areproposed according to an embodiment of the present invention.

Unlike in the method of FIG. 25, FIG. 26 shows a method for transmittinga D2D data SF within “n+k” (2601) at step S2620 when a D2D SA SF isdetermined (a subframe #n) at step S2610.

In this case, although D2D data is transmitted in a subframe right afterthe D2D SA SF, there is no problem if UE is previously notified of sucha fact.

In this case, D2D reception UE may decode the D2D data by preparing dataSF buffering received subsequently along with SA SF buffering by takinginto consideration the processing time (or processing latency).

In this case, the value “k” is configurable and may be differentlyconfigured for each piece of UE.

FIG. 27 is a diagram showing yet another example of the timing relationbetween D2D SA transmission and D2D data transmission, which is proposedaccording to an embodiment of the present invention.

That is, FIG. 27 shows a method for directly indicating a D2D data SFexplicitly through SA.

Assuming that D2D reception UE receives SA in a subframe #n at stepS2710, D2D transmission UE may calculate a value “k” based on some of SAcontents or an SA transmission resource parameter and explicitly notifythe D2D reception UE of the calculated value “k” in a subframe #n+k inwhich D2D data is received at step S2720.

A method for transmitting D2D data related to the valid period of SAcontents is described below.

SA contents may indicate an MCS value, whether frequency hopping hasbeen applied, and SA information to or in which resource allocationrelated to frequency hopping has been applied or configured in aresource region for SA transmission.

FIG. 28 is a flowchart illustrating an example of a method fortransmitting and receiving D2D data, which is proposed according to anembodiment of the present invention.

In the method of FIG. 28, if a D2D SA SF is periodically configured, itis assumed that D2D data between SA SF transmission periods istransmitted using the same SA value.

In this case, D2D reception UE that receives D2D data may receive aplurality of D2D data through the SA value once received from D2Dtransmission UE.

That is, the D2D reception UE may determine that the same one SA valueis applied to multiple data subframes.

Referring to FIG. 28, the D2D reception UE receives SA from the D2Dtransmission UE through a periodically configured SA subframe at stepS2810.

The D2D reception UE receives at least one D2D data from the D2Dtransmission UE using the received SA for a specific time interval atstep S2820.

The specific time interval may be an SA period or SA contents valid timeinterval in which the SA has been received.

The SA contents valid time interval may be previously determined, may besimply defined as an SF index, or may be defined as a multiple of an SASF period.

Furthermore, the SA contents valid time interval may be defined as acombination of an SA SF and a normal SF or may be defined as a D2D dataSF period or a multiple of the D2D data SF period.

In this case, the SF may mean a normal SF index or a D2D SF index.

In this case, if a plurality of D2D data is present for the specifictime interval, the SA includes resource allocation information relatedto the plurality of D2D data.

That is, the D2D reception UE may receive a plurality of D2D data basedon the SA received at step S2810 even without additionally receiving SAfor the specific time interval.

In another embodiment, D2D control information may be separated fromcontrol information transmitted through SA and control informationembedded (or included) in D2D data and transmitted.

That is, (1) control information, such as RA or an MCS, and (2) controlinformation, such as an NDI, may be separated through direct SA anddirect data, respectively, based on the attributes of the controlinformation and transmitted.

FIGS. 29 to 32 are diagrams showing examples of methods for providingnotification of the locations of SA resources or D2D data resources orboth, which are proposed according to embodiments of the presentinvention.

FIGS. 29 and 30 show methods for transmitting and receiving SA or D2Ddata or both using a subframe pattern in which SA resources or D2D dataresources or both may be transmitted and received.

A subframe pattern in which the SA resources or the D2D data resourcesor both may be transmitted and received may be represented as a ResourcePattern for Transmission (RPT).

The RPT means time resources or frequency resources or both forguaranteeing a plurality of transmission opportunities for D2D dataTransport Blocks (TBs).

Accordingly, the RPT may be divided into a Time-RPT (T-RPT) and aFrequency RPT (F-RPT).

Specifically, FIG. 29 shows a method for explicitly notifying D2D UE ofa subframe pattern related to SA resources or D2D data resources orboth. FIG. 30 shows a method for implicitly transmitting a subframepattern related to SA resources or D2D data resources or both to D2D UE.

UE uses some of all of UL subframes as D2D subframes.

That is, the UE performs communication with an eNB in the remaining ULsubframes other than the D2D subframes.

Accordingly, eNB-to-UE transmission and the transmission of D2D TxUE-D2D Rx UE are not generated at the same time.

If UE transmits a D2D signal to another UE in a D2D subframe, it may notreceive a D2D signal from another UE in the same band of the D2Dsubframe. The reason for this is that the D2D signal transmitted by theUE is greatly subjected to strong interference when the UE receives aD2D signal from another UE.

In order to solve such a problem, a subframe pattern (or configuration)between a D2D transmission subframe in which a D2D signal is transmittedand a D2D reception subframe in which a D2D signal is received may bedifferently configured.

Furthermore, in order to solve an interference problem attributable tothe transmission and reception of D2D signals by one UE and to reduceinterference between two pieces of adjacent UE by reducing a probabilitythat the two pieces of UE use redundant time resources at the same time,the patterns of subframes in which the two pieces of UE transmit D2Dsignals may be differently configured.

Specifically, an eNB can solve an interference problem which may begenerated between pieces of UE by configuring a subframe pattern to beused for D2D transmission by each of the pieces of UE by taking intoconsideration the distance between the pieces of UE (by checking thedegree of mutual interference).

In this case, the eNB explicitly notifies D2D UE of D2D transmissionsubframe patterns 2910 through high layer signaling, such as RRCsignaling.

In this case, the eNB may dynamically configure the D2D transmissionsubframe pattern in the D2D UE through an EPDCCH or a PDCCH. That is, ifa D2D transmission subframe pattern is transmitted to D2D UE through anEPDCCH or PDCCH, there is an advantage in that the D2D transmissionsubframe pattern can be configured by rapidly handling a change of thelocation of UE.

According to another method, in order to reduce a signaling burden of aneNB, the eNB may not determine a D2D (transmission) subframe pattern andnotify UE of the D2D (transmission) subframe, but the UE mayautonomously select a required D2D (transmission) subframe pattern.

That is, such a method is a method for implicitly obtaining, by D2D UE,a D2D subframe pattern.

In this case, the D2D UE may select the D2D subframe pattern using asimilar random method based on its own UE ID (or a UE-specific parameterhaving a similar characteristic).

In some embodiments, D2D UE may receive minimum signaling informationfrom an eNB and select a subframe pattern using a similar random methodusing the minimum signaling information as a factor for determining asimilar random value.

If such an implicit subframe pattern selection method is used, theaforementioned interference between pieces of UE can be reduced becauseproper subframe patterns (or subframe sets) are given and a subframepattern is randomly selected from the proper subframe patterns (orsubframe sets).

As shown in FIG. 29, an eNB may deliver the candidate group 2910 ofsubframe patterns related to D2D transmission, which may be potentiallyused by specific UE, through high layer signaling, such as RRCsignaling, and transmit (or designate) one or more subframe patterns2920 to be actually used for D2D transmission at a specific point oftime through an Enhanced PDCCH (EPDCCH) or a PDCCH.

Specifically, the eNB transmits previously defined N subframe patterns,that is, a candidate group of N subframe patterns (e.g., a subframepattern #0, a subframe pattern #1, a subframe pattern #2, . . . , ), toD2D UE through high layer signaling, such as RRC signaling.

Thereafter, the eNB specifies one or more of the N subframe patterns2910 as a D2D transmission subframe pattern 2920 and transmits the D2Dtransmission subframe pattern 3020 to the D2D UE through a PDCCH or anEPDCCH.

In this case, in the process for transmitting the previously defined Nsubframe patterns to the D2D UE, the eNB may assign that the actualpattern of the subframe pattern #k (k=0, 1, 2, . . . , ) has what formin the bitmap form of a subframe which is repeated in a specific cycle,for example, an SF pattern #0 (10001010) or an SF pattern #1 (00111001).

Furthermore, as shown in FIG. 30, the eNB may transmit the candidategroup 3010 of subframe patterns related to D2D transmission, which maybe potentially used, to specific UE through high layer signaling, suchas RRC signaling. D2D UE that has received the candidate group 3010 mayselect the subframe pattern 3020 to be used for actual transmission at aspecific point of time using a UE identification parameter (e.g., a UEID 3010).

In this case, the UE identification parameter (or seed) 3110 may bepreviously allocated by the eNB.

Thereafter, the D2D UE may perform D2D transmission and receptionthrough the selected subframe pattern.

FIGS. 31 and 32 are diagrams showing examples of methods for changing asubframe pattern related to SA resources or D2D data resources or both,which are proposed according to embodiments of the present invention.

FIG. 31 shows a method for explicitly providing notification of achanged subframe pattern, and FIG. 32 shows a method for implicitlyproviding notification of a changed subframe pattern.

FIGS. 31 and 32 show operations for changing, by D2D UE, a subframepattern allocated thereto using the methods of FIGS. 29 and 30.

FIGS. 31 and 32 show a subframe pattern repeated in a cycle of 8 ms(i.e., 8 subframes). An eNB may previously transmit a subframe pattern#0{10001010} and a subframe pattern #1 {00111001} 3110 to D2D UE throughhigh layer signaling.

In this case, the value “1” is a subframe related to D2D transmission,and it means that a signal related to D2D transmission may betransmitted and received in a corresponding subframe.

Furthermore, the value “0” is a subframe not related to D2Dtransmission, and this means that a signal related to D2D transmissionmay not be transmitted and received in a corresponding subframe.

The meanings of the value “0” and the value “1” may be reversed.

Thereafter, the eNB designates a D2D subframe pattern (e.g., an SFpattern #0 3120) that will be actually used by D2D UE through a PDCCH.The D2D UE operates based on the designated D2D subframe pattern.

Thereafter, the eNB transmits D2D subframe pattern change information3130, providing notification of a changed D2D subframe pattern, to theD2D UE through a PDCCH (or another piece of control information oranother message or RRC signaling) if the D2D subframe pattern has beenchanged.

The D2D subframe pattern change information may designate a changedsubframe pattern using some fields within a PDCCH or EPDCCH.

If existing DCI for an UL grant is reused for DCI for D2D, it may beused as subframe pattern change information to designate a changedsubframe pattern using a field that belongs to DCI fields and that isnot used.

The field that belongs to the DCI fields and that is not used mayinclude an indicator to determine the DCI formats 0/1A, a CQI requestfield, and an NDI field.

Some of a DM RS cyclic shift field or MCS/RV field using a plurality ofbits may be used.

If resources for SA transmission and resources for D2D data transmissionare designated to UE through a single PDCCH or EPDCCH at the same time,a subframe pattern for the SA and a subframe pattern for the D2D datamay be allocated to respective states designated by the fields withinthe DCI.

In the method of FIG. 32, D2D UE may randomly select a D2D subframepattern (e.g., an SF pattern #0 3220) that belongs to the candidategroup of D2D subframe patterns and that will be actually used using a UEID and operate based on the selected D2D subframe pattern.

In this case, an eNB may transmit a D2D subframe pattern (change)indicator, indicating that a D2D subframe pattern has been changed, tothe D2D UE through a PDCCH (or another piece of control information oranother message or RRC signaling).

In this case, the D2D UE may randomly reselect a D2D subframe pattern(e.g., an SF pattern #1 3230) using a pseudo-random selection parameter(seed, a D2D UE identification parameter) using a UE ID.

In this case, the eNB may previously notify the D2D UE of the UE IDthrough RRC signaling.

That is, if the D2D UE selects or reselects a subframe pattern using asimilar random method, the eNB may previously deliver a parameter orseed value for determining a similar random value to the D2D UE.

Furthermore, the D2D UE may determine the index of a D2D transmissionsubframe using a similar random value without a pattern.

In this case, the eNB may deliver a parameter or seed value to determinethe similar random value to the D2D UE.

Furthermore, the D2D UE may determine a subframe pattern or the index ofa subframe based on only signaling information for determining such asimilar random value. A unique value of the D2D UE may be included inthe signaling information, and the subframe pattern or the index of thesubframe may be determined.

By way of example, a method for obtaining, by D2D reception UE, thetransmission bandwidth of SA in order to detect the SA transmitted byD2D transmission UE is described below.

In this case, the transmission bandwidth of the SA may be previouslyfixed so that the D2D reception UE is aware of the transmissionbandwidth of the SA.

In this case, a portion that belongs to a resource allocation fieldincluded in an SG and that corresponds to the number of allocated RBsmay be fixed as a predetermined value, such as “0”, or may be defined asthe previously fixed transmission bandwidth of SA.

A field (or bits) included in the SG related to the transmissionbandwidth of the SA may be used for other purposes (e.g., for thepurpose of designating the location of an actual SA SF within an SA SFgroup) in addition to the transmission bandwidth of SA.

The UE scheduling of eNB-to-D2D transmission (Tx) (and/or D2D reception(Rx)) for D2D transmission is described below.

FIG. 33 is a flowchart illustrating an example of a UE scheduling methodfor D2D transmission, which is proposed according to an embodiment ofthe present invention.

First, the eNB performs a Scheduling Grant (SG) procedure along with D2Dtransmission (Tx) UE or D2D reception (Rx) UE (Step#1, S3310).

That is, the eNB transmits an SG related to D2D transmission to the D2DTx UE or the D2D Rx UE.

The SG procedure (Step#1) may be basically divided into the followingtwo methods.

(1) The first method Method#1 is a method for allocating D2Dtransmission-related resources through RRC signaling and thendynamically controlling a detailed operation, such as theactivation/release of the allocated resource, through a physical/MACcontrol channel (e.g., a PDCCH).

(2) The second method Method#2 is a method for controlling a D2Doperation by transmitting resource allocation related to D2Dtransmission or scheduling information related to D2D transmission orboth through a physical/MAC control channel.

In the methods (1) and (2), the D2D UE may receive schedulinginformation (e.g., an MCS, an RV, or a DM RS parameter) related to D2Dcommunication from the eNB and determine D2D transmission-relatedresources based on the scheduling information, or the D2D UE mayautonomously determine a D2D transmission-related resource.

Resource allocation information may be included in the schedulinginformation, and the scheduling information and the resource allocationinformation may be separately interpreted.

If the D2D UE receives scheduling information related to D2Dtransmission from the eNB according to the method (1), it may receivethe scheduling information through an RRC signal or a control channel,such as a PDCCH, or both.

In this case, if the D2D UE receives the scheduling information from theeNB through RRC signaling, the DCI format of the PDCCH may not includefields, such as an MCS, RV, and DM RS parameter related to D2Dtransmission.

Accordingly, if fields related to D2D transmission are defined to beincluded in the DCI format of a PDCCH, a total length of the DCI formatmay be reduced by obviating the unnecessary fields or a DCI format maybecome a DCI format having the same length by applying a technology,such as zero padding and transmitted.

Likewise, if the D2D UE directly determines scheduling information, suchas an MCS or an RV, contents fields related to scheduling information,such as an MCS and an RV, are not required in a PDCCH transmitted in themethod (1) or (2).

Accordingly, a method for obviating the unnecessary fields or applyingthe zero padding may be adopted.

The method (1) is described in more detail later with reference to FIG.34, and the method (2) is described in more detail later with referenceto FIG. 35.

Thereafter, the D2D transmission UE performs a scheduling procedurerelated to D2D data transmission for the transmission and reception ofD2D data along with the D2D reception UE (Step#2, S3320). That is, theD2D transmission UE performs an SA transmission procedure.

Step#2 may be used along with the methods used in Step#1.

In this case, pieces of information which may be included in SA may beas follows. In particular, pieces of information related to resourcesfor D2D data reception may be included in the SA.

Scheduling information (including resource allocation information)related to SA transmission may be construed as being transmitted fromthe eNB to the D2D transmission UE (through an SG). The SA transmissionmay be construed as being transmitted from the D2D transmission UE tothe D2D reception UE.

-   -   Information related to resources for data reception: information        related to resources for D2D data reception    -   RB allocation: RB allocation information    -   Number and pattern of retransmissions: information about the        number and pattern of retransmissions    -   Frequency hopping pattern: information about a frequency hopping        pattern    -   SPS (including periodicity) of data: information about the        periodicity of data    -   Target ID: ID information of D2D reception UE    -   MCS/RV of data    -   Timing advance of data

A method for receiving, by D2D transmission UE, an SG from an eNB anddetermining a point of time at which the D2D transmission (Tx) UEtransmits SA to D2D reception (Rx) UE is described below.

The received SG may include scheduling information (including resourceallocation information) related to the SA.

First, it is assumed that the eNB is aware of a D2D transmissionsubframe in which the D2D transmission UE may transmit the SA.

The eNB transmits the SG to the D2D transmission UE in an n−k1 (k1 is aninteger) subframe of an SA transmission subframe(n), so the D2Dtransmission UE may transmit the SA to the D2D reception UE.

The value “k1” may be about 4 when the receive processing capability ofUE is taken into consideration in an LTE (-A) system.

The value “k1” may be 2 or 3 according to the evolution of thetechnology.

The D2D transmission UE that has received the SG may also check thelocation of a D2D data transmission subframe through the received SG.

That is, the SG may be used for SA scheduling and also for a point oftime (subframe) at which D2D data is transmitted and frequency resourceallocation, which involve D2D data transmission.

A method for receiving, by D2D transmission UE, an SG from an eNB andtransmitting SA to D2D reception UE in a SA transmission-valid resourceafter a specific time is described below.

The received SG may include scheduling information related to SAtransmission.

The eNB transmits the SG to the D2D transmission UE based on a point oftime at which D2D transmission resources were requested from the D2Dtransmission UE without checking an SA transmission valid subframe indetail.

That is, when the D2D transmission UE receives the SG from the eNB, itgenerates SA based on the received SG.

Thereafter, the D2D transmission UE checks an SA-available subframe inwhich the generated SA may be transmitted and transmits the generated SAto the D2D reception UE in an available or valid D2D subframe (i.e., asubframe valid from an SA transmission viewpoint).

In this case, the D2D transmission UE receives the SG from the eNB, butmay not immediately transmit the SA to the D2D reception UE although anext subframe is available.

The reason for this is that time corresponding to “n+k2” is required inorder for the D2D transmission UE to receive the SG, perform receptionprocessing, generates SA using the SG, that is, information related tothe received SA, and prepare D2D data transmission.

In this case, k2 has an integer value. The value “k2” may be 2 or 3according to the evolution of the technology. That is, the value “k2”may have various values, such as 1, 2, 3, or 4 depending on thereception capability of UE.

If k2=4, the D2D transmission UE receives an SG from the eNB andtransmits SA to the D2D reception UE after 4 subframes.

If there is no available subframe for the SA transmission right afterthe 4 subframes, the D2D transmission UE transmits the SA to the D2Dreception UE in a next subframe.

If a next available subframe is not present, the D2D transmission UE maytransmit the SA to the D2D reception UE in a next subframe.

That is, it may be interpreted that the SA is transmitted in theearliest SA-available subframe of subframes subsequent to a subframen+4.

In this case, all of subframes not designated as D2D transmission maycorrespond to a subframe in which SA transmission is impossible.

In some embodiments, a subframe in which a synchronization signal istransmitted, such as subframes 0 and 5, may be excluded from theSA-available subframe.

In some embodiments, a subframe in which a paging subframe istransmitted, such as subframes 0, 4, 5, and 9, may also be excluded fromthe SA-available subframe.

In this case, although a specific D2D subframe (e.g., a WANsynchronization signal and a channel similar to a BCH) has beendesignated as a D2D subframe, if a channel for delivering D2D-essentialinformation is determined in a specific D2D subframe, the specific D2Dsubframe may be excluded from the SA-available subframe.

In some embodiments, a dedicated subframe for SA transmission may havebeen configured, and SA may be transmitted only in such an SA-dedicatedsubframe.

That is, the D2D transmission UE receives the SG from the eNB (in asubframe n) and may transmit the SA to the D2D reception UE in an SA(transmission)-available subframe after n+k3 subframes.

In this case, the D2D UE which has received the SG may also check thelocation of a data transmission subframe. That is, the SG may also beused for a point of time (subframe) at which data is transmitted andfrequency resource allocation, involving data transmission, in additionto SA scheduling.

Thereafter, the D2D transmission UE transmits D2D data to the D2Dreception UE based on the SA (Step#3, S3330).

In this case, the D2D transmission UE may transmit required controlinformation along with the D2D data.

The control information may be transmitted in a piggyback form alongwith the D2D data.

The validity of SG is described below.

If D2D UE receives an SG1 from an eNB and then receives an SG2 from theeNB, the D2D UE may determine that the received SG1 is no longer valid.

A point of time at which the validity of SG is determined may be appliedafter an n+k4 subframe since a subsequent transmitted SG, that is, sincethe SG2 is received (in a subframe n).

In this case, the value “k4” is an integer. If a point of time at whichthe SG2 may be applied is taken into consideration, the value “k4” mayhave a value of 2, 3, or 4.

Furthermore, the eNB may transmit the SG1 and the SG2 to the D2D UE atthe same time.

In this case, the SG1 and the SG2 may be merged into a single DCI formatand transmitted.

If separate channel coding is performed on each of the SG2 and SG2, aprobability that the D2D UE may successfully receive each SG may beincreased.

As described above, the D2D UE may feed the results of the reception ofeach SG back to the eNB and use a PUCCH as a channel for feeding theresults of the reception of each SG back.

Furthermore, control of transmission power of the D2D UE may beimplemented through the SG.

In this case, the eNB may control transmission power of the D2D UE bytransmitting a TPC command to the D2D UE using a TPC field or the DCIformats 3/3A.

If the DCI formats 3/3A are used, the eNB may reserve a specific fieldof a corresponding format for D2D power control and use the correspondformat.

This may be previously partitioned that it is for D2D power control orfor LTE (-A) power control through RRC signaling.

Furthermore, a valid time when the SG is available may be determined.

That is, after a lapse of a specific time (or a specific number ofsubframes) or after a specific number of D2D subframes since the D2D UEreceives the SG from the eNB, the D2D UE may automatically discard thereceived SG.

In some embodiments, an SG timer may be newly defined. When the SG timerexpires, an SG may be considered to be invalid.

In some embodiments, a previous SG may be defined to be valid until theD2D UE receives a next SG.

In some embodiments, after receiving an SG, the D2D UE discards thereceived SG after a specific time or a specific number of subframes. Ifanother SG has been previously received from the eNB, the D2D UE maydiscard the previously received SG although a specific time elapses.

FIG. 34 is a diagram showing an example of a UE scheduling method forD2D transmission using RRC signaling, which is proposed according to anembodiment of the present invention.

That is, FIG. 34 shows a detailed method of step S3310 in FIG. 33.

Steps S3420 and S3430 of FIG. 34 are the same as steps S3320 and S3330of FIG. 33, and thus only differences between them are described below.

First, an eNB performs a Scheduling Grant (SG) procedure along with D2DTx UE or D2D Rx UE (Step#1, S3410).

As described above with reference to FIG. 33, step S3410 may beimplemented through two methods.

(1) The first method Method#1 is a method for allocating D2Dtransmission-related resources through RRC signaling and additionallycontrolling a detailed dynamic operation for the allocated resources,such as activation/release, through a physical/MAC control channel(e.g., a PDCCH).

(2) The second method Method#2 is a method for controlling a D2Doperation by transmitting resource allocation and/or schedulinginformation related to D2D transmission through a physical/MAC controlchannel.

The method Method#1 of (1), that is, scheduling (e.g., semi-staticscheduling) for SA (and data) based on an RRC signal and a dynamiccontrol signal (e.g., an (E)PDCCH or a PHICH), is described in moredetail below.

The method (1) may be divided into 1) RRC signaling transmission foroverall resource configuration/allocation for SA (and/or data)transmission S3411 and 2) a dynamic control information transmission(S3412) method for the activation/release of SA (and data) resourcesallocated through 1).

First, RRC signaling transmission is described.

RRC Signaling: Overall Resource Configuration/Allocation for SA (andData)

As in an LTE Semi-Persistent Scheduling (SPS) scheduling method, an eNBallocates a specific resource region (or a specific resource set/group)related to D2D transmission to D2D UE through RRC signaling.

Furthermore, the eNB may allocate a monitoring resource for D2Dreception to the D2D UE in a similar way.

The specific resource region may be a subframe(s) or a set of resourceblocks.

Accordingly, the D2D UE may perform blind demodulation (or blinddecoding) on D2D data or SA by monitoring the specific resource region.

The monitoring resource may mean a resource that provides notificationof monitoring so that the D2D UE performs blind decoding on SA or D2Ddata (Tx-to-Rx for D2D) or both.

The meaning of “A and/or B” used in an embodiment of the presentinvention may be construed as having the same concept including at leastone (A, B, and A&B) of A and B.

The method (1) may be used to provide notification of a data resourceregion, that is, for D2D data scheduling in addition to SA scheduling.

That is, the method (1) means an operation for allocating resourcesrelated to D2D transmission through RRC and dynamically activating orreleasing the resources using a physical layer and an MAC layer controlchannel, like Semi-Persistent Scheduling (SPS).

For more detailed contents of the operation, reference may be made toFIGS. 28 to 32.

Thereafter, steps S3420 and S3430 are performed.

FIG. 35 is a diagram showing an example of a UE scheduling method forD2D transmission using a physical layer channel, which is proposedaccording to an embodiment of the present invention.

That is, FIG. 35 shows a detailed method of step S3310 in FIG. 33.

Steps S3520 and S3530 of FIG. 35 are the same as steps S3320 and S3330of FIG. 33, and thus only differences between them are described below.

First, an eNB performs a scheduling grant procedure along with D2D Tx UEor D2D Rx UE (Step#1, S3510).

Likewise, Step#1 may be implemented through two methods.

(1) The first method Method#1 is a method for allocating D2Dtransmission-related resources through RRC signaling and additionallycontrolling a detailed dynamic operation for the allocated resources,such as activation/release, through a physical/MAC control channel(e.g., a PDCCH).

(2) The second method Method#2 is a method for controlling a D2Doperation by transmitting resource allocation and/or schedulinginformation related to D2D transmission through a physical/MAC controlchannel.

The meaning of “A and/or B” used in an embodiment of the presentinvention may be construed as having the same concept including at leastone of A and B.

The method (2), that is, an (Enhanced) PDCCH transmission method basedon dynamic scheduling, is described below with reference to FIG. 35.

The method (2) refers to a method for notifying the D2D Tx UE (or theD2D Rx UE or both) of an MCS, an RV, an NDI, power control and/or a PMIfor D2D data demodulation in addition to resource allocation using achannel (e.g., an EPDCCH, PDCCH, PHICH, or new channel) for deliveringcontrol information in a physical layer (or including an MAC layer)instead of transmitting scheduling information (including resourceallocation) related to D2D transmission through RRC (S3511).

The resource allocation, MCS, RV, NDI, power control, or PMI may becalled to scheduling information related to D2D transmission.

Furthermore, the use of SG may be variously defined in addition to theaforementioned uses.

For example, the SG may be used to provide notification that thecontents of scheduling information related to D2D transmission have beenchanged.

The meaning of the change includes a modification, deletion, andaddition.

In this case, there are a case where the same signaling format as thatof the SG is used and a case where a signaling format different fromthat of the SG is used.

Scheduling information included in the SG may mean a change of a D2Dtransmission-related resource region in which RC signaling has beendesignated, a change of resources that need to be used by the D2D Tx UE(or the D2D Rx UE or both) in a corresponding resource region, a changeof a resource region substantially allocated by the SG, a change of aresource region group, or a change of some of or all of SA contents.

The SA contents include a variety of types of scheduling information inaddition to RA. The D2D Tx UE (or the D2D Rx UE or both) is notified ofa change of the contents of one or more of the variety of types ofscheduling information, including the RA, through the SG.

The eNB may generate a new SG of a compact type by reducing the bitfield of the SG and use the new SG.

Furthermore, as in resource reallocation related to D2D transmission, amethod for implementing SG/SA updates includes using a PHICH in additionto a PDCCH and an EPDCCH.

That is, the eNB may use PHICH resources to notify the D2D UE whetherthere is a change of an SG/SA.

The D2D UE may monitor a PHICH including information indicative of achange of an SG/SA and receive the changed SG/SA.

The D2D UE receives a modified SG/SA after a time previously designatedby the eNB or in a previously designated time interval through an SG/SAmodification notification.

In this case, the modification notification may have two meanings.

The first meaning is that the D2D UE is notified that SA will be changedand the D2D UE needs to receive the changed SA by monitoring an SG inorder to be aware of the changed SA.

The second meaning is that the D2D UE is notified that an SG has beenchanged or will be changed at a specific predetermined point of time andthus the D2D UE needs to receive the SG that has been changed or will bechanged.

As described above, the SG may be used for data scheduling in additionto SA scheduling.

Thereafter, steps S3520 and S3530 are performed.

FIG. 36 is a flowchart illustrating an example of a method forperforming an HARQ procedure for an SG, which is proposed according toan embodiment of the present invention.

Steps of S3610, S3630, and S3640 of FIG. 36 are the same as steps S3310to S3330 of FIG. 33, and thus only differences between them aredescribed below.

After step S3610, D2D UE and an eNB performs an SG Hybrid AutomaticRetransmission reQuest (HARQ) procedure at step S3620.

That is, the D2D UE may transmit a response to a received SG to the eNBbetween a point of time at which the D2D UE receives the SG from the eNBand a point of time at which the D2D UE transmits SA to another D2D UE.The response may be ACK or NACK.

As described above, the SG may be control information or resourceallocation information related to the SA or the D2D data transmission orboth, as in the activation/deactivation of allocated resources in SPS.

The control information or resource allocation information related tothe SA or the D2D data transmission or both may be indicated asscheduling information related to D2D transmission.

The SG HARQ procedure in step S3620 can prevent the deterioration ofperformance or the generation of a situation in which communication isimpossible, which is generated because the D2D UE does not transmit SAto another D2D UE or does not apply a change of SA contents that havealready been transmitted and thus continues to transmit the SA prior tothe change if the D2D UE does not receive the SG from the eNB.

Accordingly, there is a need for confirmation regarding whether an SGhas been received. In this case, an UL ACK/NACK mechanism may be used.

That is, the D2D UE may transmit a response (i.e., ACK or NACK) to theSG to the eNB using an existing PUCCH structure or in an existingembedded PUCCH to PUSCH form (i.e., in an UCI piggyback form).

In this case, if the SG complies with a mechanism, such as a PDCCH orEPDCCH format, a response to the SG may be easily used using a PUCCHresource connected to each DCI index of the PDCCH or EPDCCH.

In this case, if information included in the SG is separated intoinformation for SA scheduling and information for D2D data schedulingand received by the D2D UE, the D2D UE may feed a response regardingwhether each SG has been received back.

Furthermore, since the response to the SG may have a maximum of fourtypes, the size of the response may be represented as 1 bit to 2 bits.

In this case, the response to the SG may be fed back through a PUCCH.

Hereinafter, methods for transmitting and receiving SA and/or D2D dataproposed in this specification will be described in detail withreference to FIGS. 37 to 41.

FIG. 37 is a diagram showing a D2D operation procedure proposed in thisspecification and an example of a signaling transmission/receptionmethod related thereto.

FIG. 37 shows a D2D operation procedure in D2D communication Mode 1controlled by an eNB and a method for performing D2D communication bytransmitting and receiving information related thereto.

As illustrated in FIG. 37, an SA (Scheduling Assignment) resource pool3710 and/or data resource pool 3720 related to D2D communication may bepre-configured, and the pre-configured resource pools may be transmittedfrom an eNB to D2D UEs via high layer signaling.

The high layer signaling may be RRC signaling.

The expression ‘A and/or B’ used herein is intended to mean at least onebetween A and B, that is, A alone, B alone or A and B in combination.

The SA resource pool and/or data resource pool refers to resourcesreserved for a D2D (UE-to-UE) link or D2D communication.

The UE-to-UE link also may be called a sidelink.

Specifically, the SA resource pool refers to a resource region for SAtransmission, and the data resource pool refers to a resource region forD2D data transmission.

The SA may be transmitted in accordance with an SA periodicity 3730, andthe D2D data may be transmitted in accordance with a data transmissionperiodicity 3740.

The SA periodicity and/or the data transmission periodicity may betransmitted from the eNB to a D2D UE by a D2D grant.

Alternatively, the SA periodicity may be transmitted by a D2D grant, andthe data transmission periodicity may be transmitted by an SA.

The D2D grant refers to control information used for the eNB to transmitan SA (Scheduling Assignment) required for D2D communication to the D2DUE.

The D2D grant may be represented in DCI format 5, and carried on aphysical layer channel such as PDCCH, EPDCCH, etc., or a MAC layerchannel.

The D2D grant may contain information related to data transmission, aswell as information related to SA transmission.

For example, the SA may include RA (Resource Allocation), MCS, NDI (NewData Indicator), RV (Redundancy Version), etc.

As stated previously, the SA resource pool for SA transmission may betransmitted via RRC signaling.

Moreover, the SA may be carried on a PSCCH (Physical Sidelink ControlChannel), and the D2D data may be carried on a PSSCH (Physical SidelinkShared Channel).

A D2D transmission UE may receive SA information, particularly, resourceallocation (RA) information for SA transmission (hereinafter, ‘SA RA’),from the eNB by a D2D grant.

In this case, the D2D transmission UE may send to a D2D reception UE theSA RA information as it is received from the eNB, or may generate new SARA information with reference to the received SA RA information and thensend the newly generated SA RA information to the D2D reception UE.

If the D2D transmission UE generates new SA RA, the D2D transmission UEhas to perform SA resource allocation only within a resource region(resource pool) indicated by a D2D grant RA.

That is, only part (SA RA) of the resource region (D2D grant RA) whichthe eNB permits the use of may be selected for SA transmission.

On the contrary, the D2D transmission UE may use the D2D grant RA as itis assigned by the eNB.

In this case, however, the D2D transmission UE transmits dummy data evenif there is no D2D data to be transmitted, or occupies D2D SFs(subframes) without D2D data transmission, which may lead to a waste ofD2D SFs.

Resource pools related to D2D communication may be in the followingrelationship.

1. RRC configured D2D resource pool (A)

2. D2D grant RA indicating resource pool (B)

3. SA RA indicating resource pool (C)

If the relationship among the resource pools satisfies A>=B>=C, itprevents D2D SFs from being indiscriminately occupied for D2Dtransmission. As a result, resources for WAN data transmission may beprotected.

FIG. 38 is a flowchart showing an example of a method for transmittingdownlink control information according to an embodiment of the presentinvention.

First of all, an SA resource pool and/or D2D data resource pool areconfigured by a high layer (S3810).

Afterwards, an eNB transmits the SA resource pool and/or D2D dataresource pool to a D2D UE via high layer signaling (S3820).

Thereafter, the eNB transmits SA-related control information and/or D2Ddata-related control information separately or together to the D2Dtransmission UE by a D2D grant (S3830). The control information includesSA and/or D2D data scheduling information in the SA resource pool and/orD2D data resource pool. For example, the control information may includeRA, MCS, NDI, RV, etc.

After that, the D2D transmission UE transmits SA and/or D2D data to aD2D reception UE based on the information received in the step S3830(S3840).

The SA transmission and the D2D data transmission may be performedsimultaneously, or the D2D data transmission may be performed after theSA transmission.

Next, D2D-related resource allocation using SPS (semi-persistentscheduling) will be discussed.

In this case, D2D communication-related resources (the SA resource pooland/or data resource pool) may be reserved and allocated in advance fora D2D UE via RRC signaling, as shown in FIGS. 37 and 38.

Afterwards, the D2D UE may receive from the eNB a D2D grant indicatingwhether the reserved and allocated D2D communication-related resourcesare available.

That is, the eNB may activate the use of the resources reserved andallocated for the D2D UE through (E)PDCCH, etc. or stop or release theuse of the resources.

Here, the eNB may indicate the release of use of D2Dcommunication-related resources by setting all SA RAs to ‘0’ andtransmitting them to the D2D UE.

In another method, a specific value (e.g., ‘0’) may be set to the TPCand MCS fields to indicate the release of use of D2Dcommunication-related resources if a specific condition is met by acombination of a number of fields.

In yet another method, only the MSB (Most Significant Bit) of the MCSmay be set to ‘1’ and the other bits to ‘0’, as in ‘10000 . . . 0000’ toindicate the release of use of D2D communication-related resources.

Next, the activation/release of use of each resource type when SAresource information and D2D data resource information are separatelytransmitted will be described.

In an example, if a SA resource-related portion and a dataresource-related portion are separated within a specific field, the eNBmay indicate the activation and release of use of each resource type tothe D2D UE.

The specific field may be the TPC field, and a description will be givenby taking the TPC field as an example.

Moreover, the eNB may indicate the release of resource use fromdifferent locations by taking the SA transmission periodicity and thedata transmission periodicity into account.

This method may be implemented by transmitting different types ofinformation (SA resource information and data resource information) indifferent TPCs, or by allocating different bit sequences for two TPCs.

Alternatively, the release of resource use may be indicated by notifyingthe D2D UE of the number of the first data resource released since therelease of SA resources.

Next, a method of updating SA RAs will be described.

If a D2D UE receives SA RA information from an eNB, the point in time ofactual SA transmission by the D2D UE is in synchrony with theperiodicity of SA transmission.

Here, the eNB transmits SA RA information to the D2D UE by a D2D grantat the point in time when the D2D UE transmits an SA. Thus, the updatetime for SA RA information is in phase with the SA periodicity for SAtransmission.

Specifically, the minimum update interval of SA RA information maycorrespond with the SA periodicity.

That is, in a case where SA transmission occurs even if there is noupdate of SA RA information, the update interval of SA RA informationand the SA periodicity may be interpreted as identical.

In contrast, the update of TPC information, which corresponds totransmission power control information, may be designed differently fromthe SA RA information.

If the eNB transmits TPC information to the D2D transmission UE in everySA period, the TPC information may be updated in each SA period.

However, in view of the fact that the D2D UE can transmit multiple SAsor data in between SA periods, the update interval of the TPCinformation should be shorter than the SA periodicity in order toperform efficiently or optimize controlling power for transmission ofthe SA or data.

To this end, a DCI format for transmitting TPC information only may benewly defined, the newly defined DCI format may be transmitted inbetween SA periods.

The newly defined DCI format contains TPC information.

For example, if the SA (transmission) periodicity is 100 ms, the TPCinformation periodicity may be set to 10 ms, so that the TPC informationcan be updated in accordance with the channel state.

In this method, however, transmitting TPC information only may lead toinefficient use of resources. Thus, the eNB may transmit to the D2D UEcontrol information (e.g. HARQ information) that reflects the channelstate, together with the TPC information.

That is, the eNB may transmit TPC, HARQ, MCS, RV, PMI, etc. morefrequently at shorter intervals than the SA periods so that thisinformation can be updated to properly reflect the channel state.

Here, the above-described methods may be interpreted in a different way.

For example, the SA periodicity may be 10 ms, the actual transmission(or update) of SA RA information may occur at 100 ms intervals, andcontrol information (TPC, HARQ information, etc.) that reflects thechannel status may be generated at 10 ms intervals (or units).

That is, once the SA periodicity is set, the SA RA update periodicity,TPC update periodicity, and HARQ update periodicity may be set to aninteger multiple of the SA periodicity.

Here, the SA RA update periodicity occurs more frequently than the TPCand HARQ update periodicities.

Accordingly, the SA RA update periodicity, TPC update periodicity, andHARQ update periodicity may be preset, and may be transmitted to the D2DUE via RRC signaling.

Alternatively, the eNB may explicitly or implicitly transmit informationrelated to the SA RA update periodicity, TPC update periodicity, HARQupdate periodicity, etc. to the D2D UE by a D2D grant.

Here, the SA periodicity may be configured via RRC signaling, and theTPC periodicity and/or HARQ periodicity may be configured by a D2Dgrant.

Alternatively, the SA periodicity, TPC periodicity, and HARQ periodicitymay be set to default. That is, all the periodicities may have the samedefault value.

As previously stated, the TPC information refers to information forcontrolling the transmission power of the D2D transmission UE.

Here, the D2D transmission UE may control the transmission power forboth SA and data based on a single piece of TPC information.

Alternatively, the D2D UE controls transmission power according to thecharacteristics of each signal by taking the characteristics of SA anddata each into account.

In this case, the eNB may transmit TPC information for SA and TPCinformation for data, individually, in a D2D grant, or transmitdifferent D2D grants for different pieces of TPC information,respectively.

That is, the D2D grant may allocate the TPC information for SA and theTPC information for data to different regions.

The TPC information for SA is used to indicate the transmission powercontrol for SA, and the TPC information for data is used to indicate thetransmission power control for data.

Here, each piece of TPC information may indicate the absolute Tx powervalue or the transmission power value (delta Tx power) relative to theprevious Tx power value.

In another method, when two TPC fields (an SA TPC field and a data TPCfield) are used to control SA transmission power and data transmissionpower, the value of one of the TPC fields and an offset may be used toindicate the value of the other TPC field.

For example, if the first TPC field indicates the (absolute)transmission power value for SA and the second TPC field indicates the(absolute) transmission power value for data, the second TPC field isnot transmitted individually, but may be obtained by using a value(offset) relative to the absolute transmission power value of the firstTPC field.

That is, the first TPC field may indicate the absolute value oftransmission power for SA or data, and the second TPC field may berepresented by using an offset for the value of the first TPC field.

That is, this method is a method that indicates the relative differencein power between SA and data.

In this method, it is highly likely that changes in transmission powerbetween SA and data will occur in almost the same direction. Thus, ifthe power value is set using an offset, the transmission power for SAand data may be controlled by using fewer bits.

In general, an SA power control parameter set and a data power controlparameter set may be set independently.

That is, transmission power information for SA and D2D data are set withdifferent parameters, so they may be transmitted with different powers.

Especially, SA is more important than D2D data. Thus, the SAtransmission power may be set higher than the data transmission power,or SA may be transmitted using more resources.

Moreover, D2D data should be transmitted by taking into account HARQoperation as well as channel coding. Thus, it may be preferable that D2Ddata is controlled with different transmission power from SA.

However, even if SA and data are set to different transmission powervalues (initial values, etc.), TPC transmitted by a D2D grant may use asingle value to control the transmission power for SA and data.

In this case, even if a D2D UE receives the same TPC information fromthe eNB, the D2D UE applies different criteria for interpretation sothat the transmission power for SA and data may be calculated indifferent ways.

In this case, the different criteria the D2D UE uses to interpret thetransmission power for SA and data for a single TPC may be preset.

For example, if the transmission power for SA can be adjusted in therange from X_SA(dB) to Y_SA(dB) in a 2 bit TPC table, the transmissionpower for D2D data may be set to range from X_data to Y_data.

Although only the range of transmission power adjustment indicated bythe value of the TPC bit field has been described with an example, itmay be also possible to calculate the final transmission power for eachof different power control parameters by using different definitions,different initial values, and different default values as shown in theexample.

Next, the configuration of D2D grant RA information and SA RAinformation will be described more specifically.

Here, the D2D grant RA may refer to information related to an SA to beused for D2D communication, especially, resource allocation information,and may be represented as a SG (Scheduling Grant) or DCI format 5.

The SA RA information may refer to resource allocation informationrelated to actual SA transmission, and may be represented as PSCCH.

Specifically, the SA RA information may refer to a method as to how theD2D grant RA will be exploited for SA transmission when the D2Dtransmission UE configures (D2D-related) RA information transmitted by aD2D grant.

As previously described, assuming that there exists an RRC-configuredresource pool, the eNB selects a restricted set from the originalRRC-configured resource pool and transmits an RA to the D2D UE by a D2Dgrant.

The D2D transmission UE receives the selected D2D grant RA set from theeNB, and transmits it to a D2D reception UE as it is received orre-selects (or creates) some resources of the selected D2D grant RA setand transmits information on these resources to the D2D reception UE.

Hereinafter, a method for a D2D transmission UE to select part of an RAset received by a D2D grant and transmits the SA to a D2D reception UEthrough the selected resources will be described in detail withreference to FIG. 36.

FIG. 39 is a flowchart showing an example of a method for transmittingdownlink control information, which is proposed in this specification.

That is, FIG. 39 explains a method in which a D2D transmission UEtransmits a D2D-related packet to a D2D reception UE through resourcesselected by itself and receives a D2D-related packet from the D2Dreception UE through resources selected by itself.

First, the D2D transmission UE receives reserved and allocated resourcesrelated to D2D communication from an eNB (S3910).

The reserved and allocated resources related to D2D communication may bean SA resource pool and/or data resource pool, and may be transmittedvia RRC signaling.

Afterwards, the D2D transmission UE selects or determines some of thereserved and allocated resources related to D2D communication that areto be used for actual transmission (S3920).

Since the D2D UE usually transmits and receives a small amount of D2Dpackets, the amount of resources used by it is smaller than the amountof reserved and allocated resources (or D2D grant RA) received throughthe eNB.

Afterwards, the D2D transmission UE transmits SA and/or D2D data to theD2D transmission UE through the determined resources (S3930).

As stated above, the SA and/or D2D data may be transmittedsimultaneously, or the SA may be transmitted first and then the D2Ddata.

Here, the D2D UE may operate in Rx mode (listens to other signals) inthe resource segments not used for D2D communication, or may enter DTX(Discontinuous Transmission) state and perform energy saving or powersaving operation.

By this operation, the D2D transmission UE operating in half-duplex mayexpand the resource regions it can receive, and therefore may receiveresources from more D2D UEs.

Moreover, the D2D reception UE may monitor D2D-related resources (D2DSFs) only in particular (or restricted) SFs (subframes) and receiveresources.

In addition, the D2D reception UE also may perform energy saving byperforming DRX (Discontinuous reception) in the other D2D SFs withoutmonitoring.

Likewise, the D2D reception UE may secure more resources it can transmitto other D2D UEs, thereby increasing the opportunity of D2D transmissionand sending more D2D-related packets.

As shown in FIG. 39, in the method in which the D2D UE uses as manyresources as the number of D2D-related packets to be actuallytransmitted, the D2D transmission UE and the D2D reception UE may adjustthe size of resources transmitted or received by them as needed througha negotiation process for signal transmission and reception.

This can increase the efficiency of packet transmission between D2D UEsin a D2D network constructed entirely of meshes.

Here, in the process for adjusting the size of resources to betransmitted or received, signals transmitted or received between D2D UESmay be implemented using a high layer signal as well as a physical layersignal.

Next, a method for a D2D transmission UE to transmit an SA to a D2Dreception UE by an SA RA will be described in detail with reference toFIG. 40.

FIG. 40 is a flowchart showing an example of a method for transmittingdownlink control information according to an embodiment of the presentinvention.

FIG. 40 relates to a method in which, when there are multiple D2D datatransmission resources (or opportunities) in between SA periods, a D2Dtransmission UE notifies a D2D reception UE of the number of D2D datatransmission resources that can be used in between the SA periods.

First, as stated above, the D2D transmission UE receives SA and/or datatransmission-related resource allocation information from an eNB by aD2D grant RA (S4010).

Afterwards, the D2D transmission UE transmits configuration informationrelated to the D2D data transmission resources to the D2D reception UEby an SA (S4020).

Hereinafter, the configuration information related to the D2D datatransmission resources will be described more specifically.

The configuration information related to the D2D data transmissionresources includes indication information that indicates D2D SFs (or D2Ddata SFs) in which D2D data can be carried.

The indication information may indicate the number of contiguous D2D SFsor indicate an integer multiple of D2D SFs.

If the indication information indicates contiguous D2D SFs, the D2Dtransmission UE transmits D2D data to the D2D reception UE in contiguousK SFs immediately subsequent to an SA period (S4030).

Afterwards, the D2D transmission UE stops the transmission of D2D dataafter the contiguous K SFs (S4040).

Offset information may be used as another way to transmit D2D data.

That is, the D2D transmission UE transmits D2D data to the D2D receptionUE in contiguous K D2D SFs, starting from the SF which is at an offsetfrom an SA period, rather than the SF immediately next to the SA period,based on the offset information related to D2D data transmission, andthen may stop the transmission of D2D data in the subsequent SFs.

If the offset value is too large to secure contiguous D2D SFs within theSA period, the D2D data transmission in the non-secured SFs may beneglected or negated.

Alternatively, the D2D data transmission in the non-secured SFs may bepassed to the next SA period, and as many SFs as those not secured,starting from the first SF in the next SA period, may be designated asSFs for D2D data transmission.

Here, it is preferable that indication information (or indication bits)for indicating D2D SFs for D2D data transmission is set by taking intoaccount SA and data resource allocation periods.

For example, if the SA periodicity is 100 ms at maximum and the datatransmission periodicity is 10 ms, there are 10 opportunities for datatransmission in between the SA periods.

The number of all cases (combinations) as to how many contiguous SFs outof 10 SFs can be contiguously designated should be taken into account,and the indication information requires a field with as many bits asrequired to support all the combinations.

For example, if an indication is require for 8 cases, the indicationinformation may have a size of 3 bits, and if an indication is requiredfor 10 cases, the indication information may have a size of 4 bits.

The start position and length of an SF related to D2D data transmissionmay be indicated as another method to indicate a D2D data SF. Thismethod may be implemented by using the UL RA method of LTE(-A).

With the above method of indicating the starting position and length ofan SF related to D2D data transmission, the efficiency of resource usemay be enhanced since the number of bits of indication information canbe reduced.

Next, the use of indication information indicating the position of a D2Ddata SF in case of an increase of the SA periodicity will be described.

Specifically, if the SA periodicity increases, this may be overcome byrepeatedly transmitting indication information indicating the positionof a D2D data SF.

For example, if the SA periodicity increases to 400 ms, 4-bit indicationinformation for an SA periodicity of 100 ms and a data transmissionperiodicity of 10 ms may be re-used four times repeatedly.

Here, the eNB may notify the D2D UE of the position of the D2D data SFwhile adjusting the number of repetitions of the indication information.

The number of repetitions of a signal used for adjustment of the numberof repetitions and or of indication information indicative of theposition of the D2D data SF may be predetermined.

In this case, the predetermined value may be transmitted via RRCsignaling.

A bitmap pattern may be used as indication information indicative of theposition of a D2D data SF.

If the indication information is a bitmap pattern, the D2D data SF maybe designated very flexibly.

For example, assuming that the SA periodicity is 100 ms and the datatransmission periodicity is 10 ms, 10-bit indication information isneeded to indicate all combinations of 10 data transmission periods, asstated above.

If the SA periodicity is 400 ms and the data periodicity is 40 ms,10-bit indication information with a bitmap pattern is needed. If thedata periodicity is 10 ms, 40-bit bitmapped indication information isneeded.

However, varying the length of indication information in accordance withthe SA and/or data periodicity is difficult in the design of controlinformation.

Accordingly, it is preferable that the size of indication information,that is, the length of a bitmap, is fixed.

To this end, an SA periodicity and data transmission periodicity thatcan be used as reference are selected, and the size of indicationinformation, that is, the length of a bitmap, is determined inaccordance with the selected SA periodicity and data transmissionperiodicity.

Here, if the number of cases for indicating the position of the D2D dataSF increases due to a change in the SA periodicity and data transmissionperiodicity, the reference bitmapped indication information (referencebitmap) may be repeatedly used.

On the contrary, if the number of cases for indicating the position ofthe D2D data SF decreases, some of the combinations may be truncated.

For example, if the SA periodicity is 400 ms and the data transmissionperiodicity is 10 ms, the bitmapped indication information used with theSA periodicity of 100 ms and the data transmission periodicity of 10 msmay be used 4 times repeatedly, thereby indicating the position of theD2D data SF in accordance with the SA periodicity of 400 ms.

The bitmapped indication information used with the SA periodicity of 100ms and the data transmission periodicity of 10 ms may be referred to asreference indication information or a reference bitmap.

If the SA periodicity is 400 ms and the data transmission periodicity is20 ms, there are 20 opportunities for data transmission at 400 ms. Thus,10 bits of the reference bitmap may be repeatedly used two times,thereby indicating the position of the D2D data SF.

On the other hand, if the SA periodicity decreases to 50 ms and the datatransmission periodicity is 10 ms, only the highest 5 bits of the 10-bitbitmap indicating the D2D data SF are used (as valid information), andthe lowest 5 bits may be neglected or negated.

On the contrary to this, only the lowest 5 bits of the 10-bit bitmapindicating the D2D data SF may be used as valid information, and thehighest 5 bits may be neglected or negated.

Next, a method for reducing the number of bits of indication informationindicative of the position of a D2D data SF (or a bitmap indicative of aD2D data SF) will be described concretely with reference to FIG. 38.

FIG. 41 is a flowchart showing an example of a method for transmittingdownlink control information according to an embodiment of the presentinvention.

An eNB transmits a pre-defined (D2D) subframe pattern set to a D2Dtransmission UE by a D2D grant RA (S4110).

Afterwards, the D2D transmission UE selects one or more from thereceived subframe pattern set (S4120).

Specifically, if the eNB transmits 8 resource patterns (or subframepatterns) out of an RRC-configured D2D resource pool to the D2Dtransmission UE by a D2D grant RA, the D2D transmission UE selects oneor more from the received 8 resource patterns and transmits SA and/ordata through the selected resources.

Here, a 3-bit field or 3-bit indication information is defined in orderto represent the 8 resource patterns.

That is, the eNB may notify the D2D transmission UE of information aboutthe resource patterns by transmitting 3-bit indication information.

Here, the number of SFs for data transmission in between SA periods maybe variously selected and used by configuring the subframe patterns invarious ways (e.g., K contiguous initial subframes, an offset,interlaced SF patterns, etc.).

Afterwards, the D2D transmission UE transmits SA and/or data to the D2Dreception UE using the selected subframe pattern(s) (S4130).

In another embodiment, D2D-related resource patterns (or subframepatterns) may be hierarchically configured and transmitted to a D2D UE.

For example, the resource patterns may be hierarchically configured suchthat the RRC-configured resource pool exists in the highest layer,multiple resource patterns exist in a tree-shaped structure in thesecond highest layer, and more types of resource patterns exist in atree-shaped structure in the third highest layer.

In this case, the eNB selects one or more from the 2nd layer resourcepatterns by using RRC-configured 1st layer information and transmits theselected resource pattern(s) to the D2D transmission UE by a D2D grant.

Afterwards, the D2D transmission UE selects one from the 3rd layerresource patterns underlying the received 2nd layer resource patternsand transmits SA and/or data to a D2D reception UE.

Such a hierarchical (tree-shaped) structure of D2D resources and amethod of interpreting the same should be shared among the eNB and D2DUEs.

Next, the SA update time will be discussed.

As stated previously, upon receiving a D2D grant from the eNB, the D2Dtransmission UE transmits an SA to the D2D reception UE in accordancewith the SA periodicity by referring to the received D2D grant.

If the D2D transmission UE receives information related to a new SA fromthe eNB in between SA periods, the existing SA information is validuntil the next SA period arrives.

That is, the D2D transmission UE updates the SA in the next SAtransmission period. Then, the D2D transmission UE transmits the updatedSA to the D2D reception UE in the corresponding SA transmission period.

In this way, the method of updating new control information in the nextperiod may apply equally to TPC information, etc.

The above-described update method involves the activation of D2Dresources.

However, the release of D2D resources may be configured differently fromthe above-described activation of D2D resources.

That is, the D2D transmission UE releases D2D resources immediately uponreception of release-related information from the eNB.

Accordingly, the D2D transmission UE stops the transmission of SA and/ordata in the resources that are indicated to be released.

Specifically, when the D2D transmission UE receives informationindicative of the release of D2D resources from the eNB in between SAperiods, the D2D transmission UE releases D2D resources immediatelywithout waiting for the next SA period to arrive.

Alternatively, in a case where the SA periodicity is configured and theSA update periodicity is configured to be longer than the configured SAperiodicity, the following D2D operation may be performed.

That is, if the SA update periodicity and the SA periodicity areconfigured differently and the SA update periodicity is longer, theactivation of D2D resources may be configured for each SA update period,and the release of D2D resources may be configured for each SAtransmission, that is, for each SA period.

D2D Format for D2D Scheduling Hereinafter, the present inventionproposes a method of configuring the DCI format of a D2D grant (orsidelink grant).

In other words, the present invention proposes a method of configuringthe DCI format of a D2D grant when Mode 1 (i.e., scheduling of resourcesused for an eNB to transmit data for D2D direct communication or controlinformation) is used, out of the above-explained resource allocationmethods for D2D direct communication.

As for Mode 1, again, the eNB configures resource pools required for D2Ddirect communication. Here, the resource pools required for D2Dcommunication may be divided into a control information pool and a D2Ddata pool. When the eNB schedules control information and D2D datatransmission resources within the resource pools configured for a D2D TxUE by using a PDCCH or ePDCCH, the D2D Tx UE transmits controlinformation and D2D data using allocated resources.

The D2D Tx UE sends the eNB a request for D2D data transmissionresources, and the eNB schedules resources for transmission of controlinformation and D2D direct communication data. The transmission UEtransmits a scheduling request (SR) to the eNB, and then a BSR (BufferStatus Report) procedure is performed so that the eNB determines theamount of resources requested by the transmission UE.

D2D Rx UEs monitor the control information pool, and may selectivelydecode D2D data transmission related to the corresponding controlinformation by decoding control information related to them

As described above, a D2D grant serves to deliver control informationsuch as resource allocation, MCS, etc.,—scheduling information—requiredfor the D2D Tx UE to transmit SA and data.

As described above, the D2D control information the D2D Tx UE transmitsto the D2D Rx UE may be represented as sidelink control information(SCI). Also, the SCI may be transmitted and received through a PSCCH(Physical Sidelink Control Channel). Accordingly, in this specification,SA (Scheduling Assignment) may be used interchangeably with SCI and/orPSCCH.

Likewise, D2D data may be transmitted and received through a PSSCH(Physical Sidelink Shared Channel). Accordingly, in this specification,D2D data may be used interchangeably with PSSCH.

The DCI format for a D2D grant proposed in this specification may beused for PSCCH scheduling and PSSCH scheduling.

Also, since the D2D Tx UE and the D2D Rx UE may use an SCI for PSSCHscheduling, the DCI format for a D2D grant proposed in the presentinvention is used for PSCCH scheduling, and may include the SCI's fieldinformation.

As such, the DCI format for a D2D grant involves scheduling both SAtransmission (i.e., PSCCH) and data transmission (i.e., PSSCH). Thisrequires a large amount of control information, making it difficult toconfigure it in a single DCI format.

However, configuring it in two DCI formats, as opposed to what has beenstated above, causes a huge signaling burden. In other words, two DCIformats as shown previously in FIG. 7 may be needed to transmitscheduling information about both SA and data. That is, different DCIformats may be needed to carry both SA and data scheduling information.

As a compromise, the present invention proposes a method of schedulingboth SA and data in a single DCI format (e.g., DCI format 5) byconfiguring fields in a proper way.

To integrate these formats into one, interrelated fields may be replacedby a single integrated field and non-interrelated fields may beconfigured as discrete fields, in the process of observing thecharacteristic of D2D transmission and controlling SA transmission anddata transmission.

Hereinafter, the drawings in this specification illustrate the bitlength of each field in the DCI format for a D2D grant assuming that anuplink band (or carrier, cell, etc.) at which D2D SA and data aretransmitted is 20 MHz. Accordingly, the bit length of each field in theDCI format for a D2D grant may differ if the uplink band has a bandwidthother than 20 Hz.

Also, the bit length of each field illustrated in the drawings in thisspecification is merely an illustration for convenience of explanation,and the present invention is not limited thereto. Accordingly, the bitlength of each field may be defined differently as necessary.

Although the DCI format for a D2D grant (or sidelink grant) involvesscheduling information for both SA and data, as described above, theresource assignment/allocation (RA) field (or information) for SA andthe RA field (or information) for data may be configured separately.This will be described below with reference to FIGS. 42 and 43.

FIG. 42 is a diagram illustrating a downlink control information formataccording to an embodiment of the present invention.

Referring to FIG. 42, the DCI format for a D2D grant may includes afrequency hopping flag (FH) field 4201, a resource allocation (RA) field4202 for D2D SA, a first RA field 4203 for D2D data, a second RA field4204 for D2D data, a TPC field 4205, and zero padding (ZP) bit(s) 4206(if any).

The FH field 4201 indicates whether frequency hopping is applicable inSA and data transmissions. The FH field 4201 may apply commonly to SAtransmission and data transmission, so it may consist of a single field.

For example, if the FH field 4201 has a value of ‘1’, the D2D Tx UEperforms frequency hopping transmission during SA and datatransmissions, and if the FH field 4201 has a value of ‘0’, the D2D TxUE does not perform frequency hopping transmission during SA and datatransmissions.

The SA RA field 4202 (or PSCCH RA field, resource field for PSCCH)indicates resources information for SA transmission. That is, itindicates scheduling information (i.e., resource information) for PSCCHtransmission. Accordingly, the D2D Tx UE transmits SA (i.e., PSCCH) inthe resources indicated by the SA RA field 4202.

Here, the SA RA field 4202 may include information (or indices) forderiving the positions of time and/or frequency resource regions for SAtransmission.

For example, the SA RA field 4202 may indicate the starting position(i.e., index) in resources for SA transmission. In other words, the SARA field 4202 may indicate the starting indices of subframes and/orresource blocks in which SA is transmitted.

Moreover, the D2D Tx UE may derive time resources (for example, subframeindices) and/or frequency resources (for example, resource blockindices) for SA transmission by using a predetermined function(equation) based on the information included in the SA RA field 4202.

Resource allocation information for D2D data transmission may comprise aD2D data first RA field 4203 (or first PSSCH RA field, resource blockassignment and hopping resource allocation field) and a D2D data secondRA field 4204 (or second PSSCH RA field, time resource pattern field).

The D2D data first RA field 4203 indicates resource information (e.g.,resource blocks) for D2D data transmission in the frequency domain. Thatis, it indicates scheduling information for PSSCH transmission in thefrequency domain. Accordingly, the D2D Tx UE transmits D2D data (i.e.,PSSCH) in the frequency resources indicated by the D2D data first RAfield 4203.

For example, the D2D data first RA field 4203 may indicate the startingposition (i.e., starting resource block index) in resource blocks forD2D data transmission and a length in terms of allocated resourceblocks, by using RIV only, as in the UL RA method.

Moreover, the D2D data first RA field 4203 may indicate the startingposition (i.e., starting resource block index) and last position (i.e.,last resource block index) in resource blocks for D2D data transmission,separately by different fields (or information). In this case, more bits(e.g., 1 bit) may be required.

The D2D data second RA field 4204 indicates resource information (e.g.,subframes) used for D2D data transmission in the time domain. That is,it indicates scheduling information for PSSCH transmission in the timedomain. Accordingly, the D2D Tx UE transmits D2D data (i.e., PSSCH) inthe time resources indicated by the D2D data second RA field 4204.

For example, the D2D data second RA field 4204 may indicate a subframepattern (i.e., time resource pattern) to be used for D2D datatransmission. That is, the D2D data second RA field 4204 may includeinformation indicating a time resource pattern used for PSCCHtransmission.

Here, the D2D data second RA field 4204 may indicate any one of aplurality of predetermined time resource patterns. For example, nsubframes patterns (represented by a bitmap) are defined in advance asan SF pattern #0(10001010), SF pattern #1(00111001), . . . , SF pattern#n(10011001), and this field may indicate any one of the n definedsubframe patterns. Here, the value ‘1’ of the bitmap may mean that D2Ddata is transmitted in the corresponding subframe, and the value ‘0’ ofthe bitmap may mean that D2D data is not transmitted in thecorresponding subframe. Also, these values may mean the opposite.

The TPC field 4205 indicates the transmission power for SA and datatransmission by the D2D Tx UE. That is, it indicates transmission powerinformation for PSCCH and PSSCH.

As shown in FIG. 42, the TPC field 4205 may consist of a single field.If the TPC field 4205 consists of a single field, the value of the TPCfield 4205 applies commonly to the transmission power for SA and datatransmissions.

The ZP 4206 may be filled with control information, or not be used, ornot exist as necessary. That is, it may be omitted if not necessary.

The sequence of the fields of the DCI format and the number of bits ofeach field illustrated above are only an illustration for convenience ofexplanation, and may be changed.

As compared to the above DCI format 0 of FIG. 7, the DCI format for aD2D grant illustrated in FIG. 39 does not include the MCS field.

If the eNB notifies the D2D Tx UE of the MCS value, it is necessary thatthe MCS field exists in the DCI format for a D2D grant. However, the MCSvalue needs to be set by the D2D Tx UE itself, or needs to be providedvia high layer signaling (e.g., RRC signaling) or set to a fixed value.Accordingly, the MCS field may not be included as in FIG. 42.

Moreover, the DCI format for a D2D grant illustrated in FIG. 42 neitherincludes the NDI field nor the RV field. The NDI and RV values may beset by the D2D Tx UE itself, or provided via high layer signaling (e.g.,RRC signaling) or set to a fixed value, as is with the MCS value.

Meanwhile, the TPC field may be configured for SA and data transmissionsseparately. This will be described below with reference to FIG. 43.

FIG. 43 is a diagram illustrating a downlink control information formataccording to an embodiment of the present invention.

Referring to FIG. 43, the DCI format for a D2D grant may consist of afrequency hopping flag (FH) field 4301, a resource allocation (RA) field4302 for D2D SA, a first RA field 4303 for D2D data, a second RA field4304 for D2D data, TPC fields 4305 and 4306, and zero padding (ZP)bit(s) 4307 (if any).

As for the DCI format for a D2D grant as shown in FIG. 43, the fieldsmay be defined the same as what is illustrated previously in FIG. 42,except for the TPC fields 4305 and 4306. Now, only the differences withthe illustration of FIG. 42 will be described.

It may be preferable that TPC applies differently to SA and data. Thus,the DCI format may consist of two TPC fields 4305 and 4306, as shown inFIG. 43. That is, the DCI format may comprise a first TPC field (TPC 1)4305 indicating the transmission power for PSCCH and a second TPC field(TPC 2) 4306 indicating the transmission power for PSSCH.

Here, either of the TPC field indicating the transmission power forPSCCH and the TPC field indicating the transmission power for PSSCH maycome first. That is, the TPC field 4305 that comes first may indicatethe transmission power for SA transmission, and the TPC field 4306 thatcomes later may indicate the transmission power for data transmission,or vice versa.

In this case, the TPC fields 4305 and 4306 may include their own TPCinformation, or one of the TPC fields 4305 and 4306 may include TPCinformation and the other TPC field may include the corresponding offsetTPC information.

The sequence of the fields of the DCI format and the number of bits ofeach field illustrated above are only an illustration for convenience ofexplanation, and may be changed.

Meanwhile, the DCI format for a D2D grant may have additionalinformation such as the D2D Rx UE ID because of the D2D characteristics.This will be described below with reference to the drawings.

FIG. 44 is a diagram illustrating a downlink control information formataccording to an embodiment of the present invention.

Referring to FIG. 44, the DCI format for a D2D grant may consist of afrequency hopping flag (FH) field 4401, a resource allocation (RA) field4402 for D2D SA, a first RA field 4403 for D2D data, a second RA field4404 for D2D data, a TPC field 4405, zero padding (ZP) bit(s) 4406 (ifany), and an Rx_ID field 4407.

As for the DCI format for a D2D grant as shown in FIG. 44, the fieldsmay be defined the same as what is illustrated previously in FIG. 42,except that the Rx_ID field 4407 is added. Now, only the differenceswith the illustration of FIG. 42 will be described.

The D2D Tx UE may transmit D2D data in a unicast or multicast fashion.In this case, information for identifying a target UE or a target UEgroup is needed.

Accordingly, the Rx_ID field 4407 is used to designate a target UE or atarget UE group. That is, the Rx_ID field 4407 includes identificationinformation (i.e., target UE ID) for identifying the target UE oridentification information (i.e., target group ID) for identifying thetarget UE group.

The sequence of the fields of the DCI format and the number of bits ofeach field illustrated above are only an illustration for convenience ofexplanation, and may be changed.

Meanwhile, the DCI format for a D2D grant may further include MCSinformation. This will be described below with reference to thedrawings.

FIG. 45 is a diagram illustrating a downlink control information formataccording to an embodiment of the present invention.

Referring to FIG. 45, the DCI format for a D2D grant may consist of afrequency hopping flag (FH) field 4501, a resource allocation (RA) field4502 for D2D SA, a first RA field 4503 for D2D data, a second RA field4504 for D2D data, a TPC field 4505, zero padding (ZP) bit(s) 4506 (ifany), an MCS field 4507, and an Rx_ID field 4508.

As for the DCI format for a D2D grant as shown in FIG. 45, the fieldsmay be defined the same as what is illustrated previously in FIG. 42,except that the MCS field 4507 and the Rx_ID field 4508 are added. Now,only the differences with the illustration of FIG. 42 will be described.

The MCS field 4507 includes MCS information for D2D SA and/or datatransmission (or an index for indicating an MCS value). That is, itindicates MCS information for PSCCH and/or PSSCH.

MCS information determined by the eNB may be included in the DCI formaton the assumption that the eNB knows better about a D2D link (i.e.,sidelink) than the D2D Tx UE. For example, the eNB may estimate the D2Dlink's channel status based on a buffer status report BSR received fromthe D2D Tx UE, and determine the MCS of SA and/or data the D2D Tx UEwill transmit.

The MCS field 4507's information may be used for SA and/or datatransmission from the D2D Tx UE to the D2D Rx UE. For example, the MCSfield 4507's information may be used equally for both SA transmissionand data transmission. Also, the MCS for SA transmission may be set to afixed value, and the MCS for data transmission may be determined basedon the information indicated by the MCS field 4507.

The Rx_ID field 4508 is used to designate a target UE or a target UEgroup. That is, the Rx_ID field 4508 includes identification information(i.e., target UE ID) for identifying the target UE or identificationinformation (i.e., target group ID) for identifying the target UE group.

Although FIG. 45 illustrates that the TPC field 4505 consists of onefield, it may be divided into a TPC field for SA and a TPC field fordata and included in the DCI format, as illustrated previously in FIG.43.

The sequence of the fields of the DCI format and the number of bits ofeach field illustrated above are only an illustration for convenience ofexplanation, and may be changed.

Meanwhile, the DCI format for a D2D grant may indicate an SA resourceregion in a different way. This will be described below with referenceto the drawings.

FIG. 46 is a diagram illustrating a downlink control information formataccording to an embodiment of the present invention.

Referring to FIG. 46, the DCI format for a D2D grant may consist of afrequency hopping flag (FH) field 4601, a resource allocation (RA) field4602 for D2D SA, a first RA field 4603 for D2D data, a second RA field4604 for D2D data, an Rx_ID field 4605, a TPC field 4606, and zeropadding (ZP) bit(s) 4607 (if any).

As for the DCI format for a D2D grant as shown in FIG. 46, the fieldsmay be defined the same as what is illustrated previously in FIG. 42,except that the Rx_ID field 4607 is added and the length of the resourceallocation (RA) field 4602 is adjusted to be shorter. Now, only thedifferences with the illustration of FIG. 42 will be described.

In the resource allocation (RA) field 4602 for SA, an SA resource regionis not directly designated, but an indicator for indicating a subframepattern selected from a pre-designated subframe pattern set may beincluded. That is, it may include information indicating a time resource(e.g., subframe) pattern used for PSCCH transmission.

For example, n subframes patterns (represented by a bitmap) are definedin advance as an SF pattern #0(10001010), SF pattern #1(00111001), . . ., SF pattern #n(10011001), and this field may indicate any one of the ndefined subframe patterns. Here, the value ‘1’ of the bitmap may meanthat SA is transmitted in the corresponding subframe, and the value ‘0’of the bitmap may mean that SA is not transmitted in the correspondingsubframe. Also, these values may mean the opposite.

FIG. 46 illustrates that one subframe pattern is selected from a maximumof 8 subframe patterns. In this case, the resource allocation (RA) fieldfor SA may consist of 3 bits. However, the present invention is notlimited thereto, and the number of bits in the resource allocation (RA)field 4602 for SA may be determined depending on the total number ofsubframe patterns.

In this case, the D2D Tx UE determines frequency resources (e.g.,resource blocks) for SA transmission randomly or according to apredetermined rule, in a subframe corresponding to a subframe patternindicated by the resource allocation (RA) field 4602. Also, SA istransmitted in the determined frequency resources (e.g., resourceblocks).

The D2D Rx UE may monitor all the resource blocks for the subframecorresponding to the subframe pattern indicated by the resourceallocation (RA) field 4602 and receive SA. Also, the D2D Rx UE maymonitor frequency resources (e.g., resource blocks) determined by thepredetermined rule and receive SA.

The Rx_ID field 4605 is used to designate a target UE or a target UEgroup. That is, the Rx_ID field 4605 includes identification information(i.e., target UE ID) for identifying the target UE or identificationinformation (i.e., target group ID) for identifying the target UE group.

The sequence of the fields of the DCI format and the number of bits ofeach field illustrated above are only an illustration for convenience ofexplanation, and may be changed.

Meanwhile, an MCS field may be added to the DCI format illustrated inFIG. 46. This will be described below with reference to the drawings.

FIG. 47 is a diagram illustrating a downlink control information formataccording to an embodiment of the present invention.

Referring to FIG. 47, the DCI format for a D2D grant may consist of afrequency hopping flag (FH) field 4701, a resource allocation (RA) field4702 for D2D SA, a first RA field 4703 for D2D data, a second RA field4704 for D2D data, an MCS field 4705, a TPC field 4706, zero padding(ZP) bit(s) 4707 (if any), and an Rx_ID field 4708.

As for the DCI format for a D2D grant as shown in FIG. 47, the fieldsmay be defined the same as what is illustrated previously in FIG. 46,except that the MCS field 4705 is added. Now, only the differences withthe illustration of FIG. 46 will be described.

As explained previously, the eNB may estimate the D2D link's channelstatus based on a BSR received from the D2D Tx UE, and determine the MCSof SA and/or data the D2D Tx UE will transmit.

The MCS field 4705's information may be used for SA and/or datatransmission from the D2D Tx UE to the D2D Rx UE. For example, the MCSfor SA transmission may be set to a fixed value, and the MCS for datatransmission may be determined based on the information indicated by theMCS field 4705.

The sequence of the fields of the DCI format and the number of bits ofeach field illustrated above are only an illustration for convenience ofexplanation, and may be changed.

Meanwhile, the DCI format for a D2D grant may further include DMRS(demodulation reference signal) CS (cyclic shift) information. This willbe described below with reference to the drawings.

FIG. 48 is a diagram illustrating a downlink control information formataccording to an embodiment of the present invention.

Referring to FIG. 48, the DCI format for a D2D grant may consist of afrequency hopping flag (FH) field 4801, a resource allocation (RA) field4802 for D2D SA, a first RA field 4803 for D2D data, a second RA field4804 for D2D data, an MCS field 4805, a TPC field 4806, zero padding(ZP) bit(s) 4807 (if any), a DMRS CS field 4808, and an Rx_ID field4809.

As for the DCI format for a D2D grant as shown in FIG. 48, the fieldsmay be defined the same as what is illustrated previously in FIG. 47,except that the DMRS CS field 4808 is added. Now, only the differenceswith the illustration of FIG. 47 will be described.

The DMRS CS field 4808 includes DMRS CS information for SA and/ordemodulation. That is, the DMRS CS field 4808 may include a CS value (oran index for indicating it) for identifying a DMRS. Also, the DMRS CSfield 4903 may include orthogonal cover code (OCC) information, alongwith the CS value, or may include an index for indicating it.

DMRS refers to a signal for demodulating SA and/or data transmitted bythe D2D Tx UE. A cyclically shifted DMRS sequence may be generated bycyclically shifting a base sequence by the CS value indicated by theDMRS CS field 4808. Also, DMRS may be mapped and transmitted on the sameresource region (e.g., resource blocks) where SA and/or data istransmitted.

The sequence of the fields of the DCI format and the number of bits ofeach field illustrated above are only an illustration for convenience ofexplanation, and may be changed.

Meanwhile, the foregoing FIGS. 42 through 48 illustrate that the RAfield for SA and the RA field for data are configured separately and theinformation included in the respective RA fields indicates resources forSA and resources for data, respectively.

It should be noted that the RA information for SA transmission and theRA information for data may correlate to each other.

Assuming that the RA field for SA is ‘RA 1’ and the RA fields for data(the first RA field for D2D data and/or second RA field for D2D data asshown in FIGS. 42 through 48) are ‘RA 2’, transmission may occur in sucha manner that RA 1 indicates the position of a SA resource region andinformation obtained by a combination of RA 1 and RA 2 indicates theposition of a data resource region.

That is, the correlation between the SA and data resource regions may betaken into account and used for RA field configuration to configureindication bits in such a manner as to involve the correlation betweenthe RA field information.

In this case, the D2D Tx UE may determine the SA resource region basedon the information included in the RA 1 field and determine the dataresource region based on the information obtained by the combination ofthe RA 1 field and the RA 2 field.

On the contrary, transmission may occur in such a manner that RA 2indicates the position of a data resource region and informationobtained by a combination of RA 1 and RA 2 indicates the position of aSA resource region.

In this case, the D2D Tx UE may determine the data resource region basedon the information included in the RA 2 field and determine the SAresource region based on the information obtained by the combination ofthe RA 1 field and the RA 2 field.

More specifically, for example, the RA 2 field may indicate the resourceregions (positions of time/frequency resources for data transmission) tobe actually transmitted, and the RA 1 field may indicate the positionsof resources for SA transmission, which are at a certain offset from thepositions of time/frequency resources in the RA 2 field, that is, offsetinformation. Contrariwise, the RA 1 field may indicate the positions ofresource regions for SA transmission, and the RA 2 field may indicatethe positions of resources for data transmission, which are at a certainoffset from the positions of resources in the RA 1 field, that is,offset information.

Meanwhile, the RA field for D2D SA transmission may be omitted from theDCI format for a D2D grant. This will be described below with referenceto the drawings.

FIG. 49 is a diagram illustrating a downlink control information formataccording to an embodiment of the present invention.

Referring to FIG. 49, the DCI format for a D2D grant may consist of afrequency hopping flag (FH) field 4901, an MCS field 4902, a DMRS CSfield 4903, a first RA field 4904 for D2D data, a second RA field 4905for D2D data, a TPC field 4906, and zero padding (ZP) bit(s) 4907 (ifany).

The FH field 4901 indicates whether frequency hopping is applicable inSA and data transmission. The FH field 4901 may apply commonly to SAtransmission and data transmission, so it may consist of a single field.

The MCS field 4902 includes an MCS value for D2D SA and/or datatransmission (or an index for indicating the MCS value).

The MCS field 4902's information may be used for SA and/or datatransmission from the D2D Tx UE to the D2D Rx UE. For example, the MCSfield 4902's information may be used equally for both SA transmissionand data transmission. Also, the MCS for SA transmission may be set to afixed value, and the MCS for data transmission may be determined basedon the information indicated by the MCS field 4902.

The DMRS CS field 4903 may include a CS value (or an index forindicating it) for identifying a DMRS. Also, the DMRS CS field 4903 mayinclude orthogonal cover code (OCC) information, along with the CSvalue, or may include an index for indicating it.

A cyclically shifted DMRS sequence may be generated by cyclicallyshifting a base sequence by the CS value indicated by the DMRS CS field4903. Also, DMRS may be mapped and transmitted on the same resourceregion (e.g., resource blocks) where SA and/or data is transmitted.

Resource allocation information for D2D data transmission may comprise aD2D data first RA field 4904 (or first PSSCH RA field, resource blockassignment and hopping resource allocation field) and a D2D data secondRA field 4905 (or second PSSCH RA field, time resource pattern field).

The D2D data first RA field 4904 indicates resource information (e.g.,resource blocks) for D2D data transmission in the frequency domain. Thatis, it indicates scheduling information for PSSCH transmission in thefrequency domain. Accordingly, the D2D Tx UE transmits D2D data (i.e.,PSSCH) in the frequency resources indicated by the D2D data first RAfield 4904.

For example, the D2D data first RA field 4904 may indicate the startingposition (i.e., starting resource block index) in resource blocks forD2D data transmission and a length in terms of allocated resourceblocks, by using RIV only, as in the UL RA method.

Moreover, the D2D data first RA field 4904 may indicate the startingposition (i.e., starting resource block index) and last position (i.e.,last resource block index) in resource blocks for D2D data transmission,separately by different fields.

The D2D data second RA field 4905 indicates resource information (e.g.,subframes) used for D2D data transmission in the time domain. That is,it indicates scheduling information for PSSCH transmission in the timedomain. Accordingly, the D2D Tx UE transmits D2D data (i.e., PSSCH) inthe time resources indicated by the D2D data second RA field 4905.

For example, the D2D data second RA field 4905 may indicate a subframepattern (i.e., time resource pattern) to be used for D2D datatransmission. That is, it may indicate any one of a plurality ofpredetermined time resource patterns.

The time/frequency resource regions for SA transmission may not beconfigured. That is, the D2D Tx UE may randomly select resources from anSA resource pool configured via high layer signaling (e.g., RRCsignaling) and transmit SA. In this case, the D2D Rx UE may monitor theentire SA resource pool and receive SA from the D2D Tx UE.

Moreover, the positions of time/frequency resource regions for SAtransmission may be derived from the time/frequency resources for datatransmission. For example, the positions of time/frequency resourceregions for SA transmission may be derived from the time/frequencyresources for data transmission according to a predetermined rule or byusing predetermined offset values.

The TPC field 4906 indicates the transmission power for SA and datatransmissions by the D2D Tx UE.

The ZP 4907 may be filled with control information, not be used, or notexist as necessary. That is, it may be omitted if not necessary.

The sequence of the fields of the DCI format and the number of bits ofeach field illustrated above are only an illustration for convenience ofexplanation, and may be changed.

FIG. 50 is a diagram illustrating a downlink control information formataccording to an embodiment of the present invention.

Referring to FIG. 50, the DCI format for a D2D grant may consist of afrequency hopping flag (FH) field 5001, an MCS field 5002, a DMRS CSfield 5003, a first RA field 5004 for D2D data, a second RA field 5005for D2D data, a TPC field 5006, zero padding (ZP) bit(s) 5007 (if any),and an Rx_ID field 5008.

As for the DCI format for a D2D grant as shown in FIG. 50, the fieldsmay be defined the same as what is illustrated previously in FIG. 49,except that the Rx_ID field 5008 is added. Now, only the differenceswith the illustration of FIG. 49 will be described.

The Rx_ID field 5008 is used to designate a target UE or a target UEgroup. That is, the Rx_ID field 5008 includes identification information(i.e., target UE ID) for identifying the target UE or identificationinformation (i.e., target group ID) for identifying the target UE group.

The sequence of the fields of the DCI format and the number of bits ofeach field illustrated above are only an illustration for convenience ofexplanation, and may be changed.

Devices in General to which the Present Invention is Applicable

FIG. 51 illustrates a block diagram of a wireless communication deviceaccording to an embodiment of the present invention.

Referring to FIG. 51, a wireless communication system includes an eNB5110 and a plurality of UEs 5120 located within the eNB 5110's coverage.

The eNB 5110 includes a processor 5111, a memory 5112, and an RF unit(radio frequency unit) 5113. The processor 5111 implements thefunctions, processes and/or methods proposed previously with referenceto FIGS. 1 through 50. Layers of a radio interface protocol may beimplemented by the processor 5111. The memory 5112 is connected to theprocessor 5111 and stores various information for driving the processor5111. The RF unit 5113 is connected to the processor 5111 and transmitsand/or receives radio signals.

The UEs 5120 each include a processor 5121, a memory 5122, and an RFunit 5123. The processor 5121 implements the functions, processes and/ormethods proposed previously through FIGS. 1 through 50. Layers of aradio interface protocol may be implemented by the processor 5121. Thememory 5122 is connected to the processor 5121 and stores variousinformation for driving the processor 5121. The RF unit 5123 isconnected to the processor 5121 and transmits and/or receives radiosignals.

The memories 5112 and 5122 may be located inside or outside theprocessors 5111 and 5121, and connected to the processors 5111 and 5121by various well-known means. Also, the eNB 5110 and/or the UEs 5120 eachmay have a single antenna or multiple antennas.

In the aforementioned embodiments, the elements and characteristics ofthe present invention have been combined in specific forms. Each of theelements or characteristics may be considered to be optional unlessotherwise described explicitly. Each of the elements or characteristicsmay be implemented in such a way as not to be combined with otherelements or characteristics. Furthermore, some of the elements and/orthe characteristics may be combined to form an embodiment of the presentinvention. Order of operations described in connection with theembodiments of the present invention may be changed. Some of theelements or characteristics of an embodiment may be included in anotherembodiment or may be replaced with corresponding elements orcharacteristics of another embodiment. It is evident that in the claims,one or more embodiments may be constructed by combining claims nothaving an explicit citation relation or may be included as one or morenew claims by amendments after filing an application.

An embodiment of the present invention may be implemented by variousmeans, for example, hardware, firmware, software or a combination ofthem. In the case of implementations by hardware, an embodiment of thepresent invention may be implemented using one or moreApplication-Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers and ormicroprocessors or all of them.

In the case of implementations by firmware or software, an embodiment ofthe present invention may be implemented in the form of a module,procedure, or function for performing the aforementioned functions oroperations. Software code may be stored in the memory and driven by theprocessor. The memory may be placed inside or outside the processor, andmay exchange data with the processor through a variety of known means.

It is evident to those skilled in the art that the present invention maybe materialized in other specific forms without departing from theessential characteristics of the present invention. Accordingly, thedetailed description should not be construed as being limitative fromall aspects, but should be construed as being illustrative. The scope ofthe present invention should be determined by reasonable analysis of theattached claims, and all changes within the equivalent range of thepresent invention are included in the scope of the present invention.

INDUSTRIAL APPLICABILITY

While a method for transmitting control information in D2D communicationin a wireless communication system according to the present inventionhas been described with an example applicable to 3GPP LTE/LTE-A systems,it also may be applicable to a variety of wireless communicationsystems.

1. A method for receiving downlink control information in a wirelesscommunication system supporting D2D (Device-to-Device) communication,the method comprising: receiving, by a UE, downlink control informationfor D2D communication from an eNB; transmitting, by the UE to areception UE, D2D communication control information on a PSCCH (PhysicalSidelink Control Channel) based on the downlink control information; andtransmitting, by the UE to the reception UE, D2D communication data on aPSSCH (Physical Sidelink Shared Channel) based on the downlink controlinformation, wherein the downlink control information comprises: ahopping flag field indicating whether frequency hopping is applicablewhen transmitting the D2D communication data; a PSCCH resourceallocation (RA) field including scheduling information for the PSCCH; afirst PSSCH RA field including scheduling information for the PSSCH in afrequency domain; a second PSSCH RA field including schedulinginformation for the PSSCH in a time domain; and a TPC (TransmissionPower Control) field including transmission power information for thePSCCH and PSSCH.
 2. The method of claim 1, wherein the PSCCH RA fieldincludes index information for deriving the positions of resourceregions for PSCCH transmission.
 3. The method of claim 1, wherein thefirst PSSCH RA field includes a starting resource block index for PSSCHtransmission and a length in terms of allocated resource blocks.
 4. Themethod of claim 1, wherein the second PSSCH RA field includesinformation indicating a time resource pattern used for PSSCHtransmission.
 5. The method of claim 1, wherein the TPC field comprisesa first TPC field indicating the transmission power for PSCCH and asecond TPC field indicating the transmission power for PSSCH.
 6. Themethod of claim 1, wherein the downlink control information furtherincludes an RX_ID field including identification information for thereception UE.
 7. The method of claim 1, wherein the downlink controlinformation further includes an MCS field indicating MCS (ModulationCoding and Scheme) information for PSCCH and/or PSSCH transmission. 8.The method of claim 1, wherein the PSCCH RA field includes informationindicating a time resource pattern used for PSCCH transmission.
 9. Themethod of claim 1, wherein the downlink control information furtherincludes a DMRS CS field including DMRS (demodulation reference signal)CS (cyclic shift) information for demodulating the D2D communicationcontrol information and/or D2D communication data.
 10. (canceled)
 11. Amethod for transmitting downlink control information in a wirelesscommunication system supporting D2D (Device-to-Device) communication,the method comprising: transmitting, by an eNB to a UE, downlink controlinformation for D2D communication, wherein the downlink controlinformation comprises: a hopping flag field indicating whether frequencyhopping is applicable when transmitting the D2D communication data; aPSCCH resource allocation (RA) field including scheduling informationfor the PSCCH; a first PSSCH RA field including scheduling informationfor the PSSCH in a frequency domain; a second PSSCH RA field includingscheduling information for the PSSCH in a time domain; and a TPC(Transmission Power Control) field including transmission powerinformation for the PSCCH and PSSCH.
 12. The method of claim 11, whereinthe PSCCH RA field includes index information for deriving the positionsof resource regions for PSCCH transmission.
 13. The method of claim 11,wherein the first PSSCH RA field includes a starting resource blockindex for PSSCH transmission and a length in terms of allocated resourceblocks.
 14. The method of claim 11, wherein the second PSSCH RA fieldincludes information indicating a time resource pattern used for PSSCHtransmission.
 15. (canceled)